Yugoslav Front The Yugoslav Front , also known as the National Liberation War , was a complex conflict that took place during World War II ( 1941 – 1945 ) in occupied Yugoslavia . The war began after the Kingdom of Yugoslavia was overrun by Axis forces and partitioned between Germany , Italy , Hungary , Bulgaria and client regimes . Primarily it was a guerilla liberation war fought by the communist - led , republican Yugoslav Partisans against the Axis occupying forces and their locally - established puppet regime s , such as the Independent State of Croatia and the Government of National Salvation . At the same time , it was a civil war between the Partisans and the Serbian royalist Chetnik movement , which collaborated extensively with the Axis powers . Both the Yugoslav Partisans and the Chetnik movement initially resisted the occupation . However , after 1941 , the Chetniks adopted a " policy of collaboration . " They collaborated extensively and systematically with the Italian occupation forces until the Italian capitulation , and thereon also with German and Ustaše forces . The Axis mounted a series of offensives intended to destroy the Partisans , coming close to doing so in winter and spring of 1943 . Despite the setbacks , the Partisans remained a credible fighting force , gaining recognition from the Western Allies and laying the foundations for the post - war Yugoslav state . With support in logistics , equipment , training , and air power from the Western Allies , and Soviet ground troops in the Belgrade Offensive , the Partisans eventually gained control of the entire country and of border regions of Italy and Austria . The human cost of the war was enormous . The number of war victims is still in dispute , but is generally agreed to have been at least one million . Non - combat victims included the majority of the country ' s Jewish population , many of whom perished in concentration and extermination camp s ( e . g . Jasenovac , Banjica ) run by the client regimes . In addition , the Croatian Ustaše regime committed genocide against local Serbs and Roma , the Chetniks pursued ethnic cleansing against the Muslim and Croat population , and Italian occupation authorities against Slovenes . German troops also carried out mass executions of civilians in retaliation for resistance activity ( Kragujevac massacre ) . Finally , during and after the final stages of the war , Yugoslav authorities and Partisan troops carried out reprisals , including the deportation of the Danube Swabian population , forced marches and executions of thousands of captured collaborators and civilians fleeing their advance ( Bleiburg massacre ) , and atrocities against the Italian population in Istria ( Foibe killings ) . Background . On 6 April 1941 the Kingdom of Yugoslavia was invaded from all sides by the Axis powers , primarily by German forces , but also Italian Fascists , and their Hungarian and Bulgarian collaborators elsewhere . During the invasion , Belgrade was bombed by the German air force ( " Luftwaffe " ) . The invasion lasted little more than ten days , ending with the unconditional surrender of the Royal Yugoslav Army on 17 April . Besides being hopelessly ill - equipped when compared to the German army ( " Wehrmacht Heer " ) , the Yugoslav army attempted to defend all borders but only managed to thinly spread the limited resources available . Also , large numbers of the population refused to fight , instead welcoming the Germans as liberators from government oppression . However , as this meant each individual nationality would turn to movements opposed to the unity promoted by the South Slavic state , two different concepts of resistance emerged , the monarchist Chetniks , and the communist Partisans . The main reason was that neither of two of the constituent national groups ( Slovenes and Croats ) were prepared to fight in defense of a Yugoslav state with a continued Serb monarchy . The only effective opposition to the invasion was from units wholly within Serbia itself . The Serbian General Staff were united on the question of Yugoslavia as a " Greater Serbia " , ruled , in one way or another , by Serbia . On the eve of the invasion , there were 165 generals on the Yugoslav active list . Of these , all but four were Serbs . The terms of the capitulation were extremely severe , as the Axis proceeded to dismember Yugoslavia . Germany occupied northern Slovenia , while retaining direct occupation over a rump Serbian state and considerable influence over its newly created puppet state , the Independent State of Croatia , which extended over much of today ' s Croatia and contained all of modern Bosnia and Herzegovina . Mussolini ' s Italy gained the remainder of Slovenia , Kosovo , and large chunks of the coastal Dalmatia region ( along with nearly all of the Adriatic islands and the Bay of Kotor ) . It also gained control over the newly created Montenegrin puppet state , and was granted the kingship in the Independent State of Croatia , though wielding little real power within it . Hungary dispatched the Hungarian Third Army to occupy Vojvodina in northern Serbia , and later forcibly annexed sections of Baranja , Bačka , Međimurje , and Prekmurje . Bulgaria , meanwhile , annexed nearly all of the modern - day Republic of Macedonia . After the capitulation of Italy in 1943 , all territories under its administration were placed under German or Ustaše control . These included Kosovo , Albania , Montenegro , and much of Dalmatia . The fall of a true international body following the split in affinity by the world ' s nations , the status of international law and questions of continuity from former conventions became a shady matter . The government in exile was now only recognized by the Allied powers . The Axis had recognized the territorial acquisitions of their allied states . When the AVNOJ ( the Partisan wartime council in Yugoslavia ) was eventually recognized by the Allies , by late 1943 , the official recognition of the Partisan Democratic Federal Yugoslavia soon followed . The National Liberation Army of Yugoslavia was recognized by the major Allied powers at the Tehran Conference , when United States agreed to the position of other Allied . The newly recognized Yugoslav government , headed by Prime Minister Josip Broz Tito , was a joint body formed of AVNOJ members and the members of the former government - in - exile in London . The resolution of a fundamental question , whether the new state remained a monarchy or was to be a republic , was postponed until the end of the war , as was the status of King Peter II . Yugoslav resistance . From the start , the Yugoslav resistance forces consisted of two factions : the Partisans , a communist - led movement propagating pan - Yugoslav tolerance ( " brotherhood and unity " ) and incorporating republican , left - wing and liberal elements of Yugoslav politics , on one hand , and the Chetniks , a conservative royalist and nationalist force , enjoying support almost exclusively from the Serbian population in occupied Yugoslavia , on the other hand . Initially the Chetniks received recognition from the Western Allies , while the Partisans were supported by the Soviet Union . The Partisans gained universal Allied recognition at the Tehran Conference in 1943 , by which time the degree of Chetnik collaboration with the Axis was widespread . The Yugoslav Partisans ( officially the People ' s Liberation Army and Partisan Detachments of Yugoslavia , NOV i POJ ) , under the command of Marshal Josip Broz Tito , primarily fought against the German , Italian , Hungarian , Bulgarian , and collaborationist forces . Drawing on the experienced fighters from the Spanish Civil War and , in Slovenia , on the TIGR members to train troops , and on socialist ideology to win support that crossed national lines , they steadily gained power during the struggle , winning recognition from the Allies and the Yugoslavian government in exile as the legitimate Yugoslav liberation force . The movement grew to become the largest resistance force in occupied Europe , with 800 , 000 men organized in 4 field armies . Eventually the Partisans prevailed against all of their opponents as the official army of the newly founded Democratic Federal Yugoslavia ( later Socialist Federal Republic of Yugoslavia ) . Although the activity of the Macedonian and Slovene Partisans were part of the Yugoslav People ' s Liberation War , the specific conditions in Macedonia and Slovenia , due to the strong autonomist tendencies of the local communists , led to the creation of a separate sub - armies called the People ' s Liberation Army of Macedonia , and Slovene Partisans led by Liberation Front of the Slovene People , respectively . In 1944 , the Macedonian and Serbian commands made contact in southern Serbia and formed a joint command , which consequently placed the Macedonian Partisans under the direct command of Marshal Josip Broz Tito . The Slovene Partisans also merged with Tito ' s forces in 1944 . The autonomist wing in the Communist Party of Macedonia , which dominated during World War II , was finally pushed aside in 1945 after the Second Assembly of the ASNOM . The royalist Chetniks ( officially the Yugoslav Army in the Fatherland , JVUO ) , under the command of General Draža Mihailović , drew primarily from the scattered remnants of the Royal Yugoslav Army , relying overwhelmingly on the ethnic Serbian population for support . They were formed soon after the invasion of Yugoslavia and the surrender of the government on 17 April 1941 . The Chetniks were initially the only resistance movement recognized by the Yugoslavian government in exile and the Western Allies . The Partisans and Chetniks attempted to cooperate early during the conflict , but this quickly fell apart . After fruitless negotiations , the Chetnik leader , General Mihailović , turned against the Partisans as his main enemy . According to him , the reason was humanitarian : the prevention of German reprisals against Serbs . This however , did not stop the activities of the Partisan resistance , and Chetnik units attacked the Partisans in November 1941 , while increasingly receiving supplies and cooperating with the Germans and Italians in this . The British liaison to Mihailović advised London to stop supplying the Chetniks after the Užice attack ( see First anti - Partisan offensive ) , but Britain continued to do so . Guerrilla and civil war . Early resistance . From 1931 til 1939 , the USSR prepared Communists for the partisan war in Yugoslavia . On the eve of the war , hundreds of future prominent Yugoslav communist leaders completed special " partisan courses " organized by the Soviet military intelligence in the Soviet Union and Spain . Operation Barbarossa , the Axis invasion of the Soviet Union , began on 22 June 1941 . On the same day , Yugoslav Partisans formed the 1st Sisak Partisan Detachment , was the first armed anti - fascist resistance unit formed by a resistance movement in occupied Yugoslavia during World War II . Founded in the Brezovica forest near Sisak , Croatia , its creation marked the beginning of anti - Axis resistance in occupied Yugoslavia . Various military formations more or less linked to the general liberation movement were involved in armed confrontations with Axis forces which erupted in various areas of Yugoslavia in the ensuing weeks . The Communist Party of Yugoslavia formally decided to launch an armed uprising on 4 July 1941 , a date which was later marked as Fighter ' s Day – a public holiday in the Socialist Federal Republic of Yugoslavia . One Žikica Jovanović Španac ( " The Spaniard " ) shot the first bullet of the campaign on 7 July 1941 , later the Day of State of the Socialist Republic of Serbia ( part of SFR Yugoslavia ) . On 10 August 1941 in Stanulović , a mountain village , the Partisans formed the Kopaonik Partisan Detachment Headquarters . Their liberated area , consisting of nearby villages and called the " Miners Republic " , was the first in Yugoslavia , and lasted 42 days . The resistance fighters formally joined the ranks of the Partisans later on . In September 1941 , Partisans organized a sabotage at the General Post Office in Zagreb . On 22 December 1941 the Partisans formed the 1st Proletarian Assault Brigade ( " 1 . Proleterska Udarna Brigada " ) – the first regular Partisan military unit capable of operating outside its local area . 22 December became the " Day of the Yugoslav People ' s Army " . In 1942 Partisan detachments officially merged into the People ' s Liberation Army and Partisan Detachments of Yugoslavia ( NOV i POJ ) . The Chetnik movement was organized after the surrender of the Royal Yugoslav Army by some of the remaining Yugoslav soldiers . This force was organized in the Ravna Gora district of western Serbia under Colonel Draža Mihailović . However , unlike the Partisans , Mihailović ' s forces were almost entirely ethnic Serbs . He directed his units to arm themselves and await his orders for the final push . Mihailović avoided direct action against the Axis , which he judged were of low strategic importance . The Chetniks initially enjoyed the support of the Western Allies up to the Tehran Conference ( 1943 ) . In 1942 , " Time Magazine " featured an article which praised the " success " of Mihailović ' s Chetniks and heralded him as the sole defender of freedom in Nazi - occupied Europe . The Chetniks also were praised for saving 500 downed Allied pilots . However , Tito ' s Partisans fought the Germans more actively during this time . Tito and Mihailović had a bounty of 100 , 000 Reichsmarks offered by Germans for their heads . While " officially " remaining mortal enemies of the Germans and the Ustaše , the Chetniks were known for making clandestine deals with the Italians and other occupying forces . Axis response . The Partisans fought an increasingly successful guerrilla campaign against the Axis occupiers and their local collaborators , the Serbian Government of National Salvation , the Ustaše - controlled Independent State of Croatia , and the Chetniks ( which they also considered collaborators ) . They enjoyed gradually increased levels of success and support of the general populace , and succeeded in controlling large chunks of Yugoslav territory . People ' s committees were organized to act as civilian governments in areas of the country liberated by the Partisans . In places , even limited arms industries were set up . At the very beginning , however , the Partisan forces were relatively small , poorly armed , and without any infrastructure . But they had two major advantages over other military and paramilitary formations in former Yugoslavia : the first and most immediate advantage was a small but valuable cadre of Spanish Civil War veterans . Unlike some of the other military and paramilitary formations , these veterans had experience with a modern war fought in circumstances quite similar to those found in World War II Yugoslavia . Their other major advantage , which became more apparent in later stages of War , was in the Partisans being founded on ideology rather than ethnicity . Therefore they could expect at least some levels of support in almost any corner of the country , unlike other paramilitary formations limited to territories with Croat or Serb majority . This allowed their units to be more mobile and fill their ranks with a larger pool of potential recruits . During the war , generally the national minorities , with the exception of Czechs , Slovaks and Turks cooperated with the occupation forces . The Axis powers , however , were quite aware of the Partisan threat . The most numerous local force , besides the four second - line German Wehrmacht infantry divisions assigned to occupation duties was the Croatian Home Guard , founded in April 1941 , a few days after the founding of the Independent State of Croatia ( NDH ) itself . It was done with the authorisation of German occupation authorities . The task of the new Croatian armed forces was to defend the new state against both foreign and domestic enemies . The Croatian Home Guard was originally limited to 16 infantry battalions and 2 cavalry squadrons – 16 , 000 men in total . The original 16 battalions were soon enlarged to 15 infantry regiments of two battalions each between May and June 1941 , organised into five divisional commands , some 55 , 000 enlisted men . Support units included 35 light tanks supplied by Italy , 10 artillery battalions ( equipped with captured Royal Yugoslav Army weapons of Czech origin ) , a cavalry regiment in Zagreb and an independent cavalry battalion at Sarajevo . Two independent motorized infantry battalions were based at Zagreb and Sarajevo respectively . Several regiments of Ustaše militia were also formed at this time , which operated under a separate command structure to , and independently from , the Croatian Home Guard , until the units of the Ustaše militia and Croatian Home Guard were reorganized and combined in November 1944 to form the Army of the Independent State of Croatia . The fledgling Army crushed the revolt by Serbs in Eastern Herzegovina in June 1941 , and fought in July in Eastern and Western Bosnia . They fought in Eastern Herzegovina again , when Croatian - Dalmatian and Slavonian battalions reinforced local units . The Home Guard reached its maximum size at the end of 1943 , when it had 130 , 000 men . The Croatian Home Guard also included an air force , the Air Force of the Independent State of Croatia ( " Zrakoplovstvo Nezavisne Države Hrvatske " , or ZNDH ) , the backbone of which was provided by 500 former Royal Yugoslav Air Force officers and 1 , 600 NCOs with 125 aircraft . By 1943 the ZNDH was 9 , 775 strong and equipped with 295 aircraft . As the levels of resistance to its occupation grew , the Axis Powers responded with numerous minor offensives . There were also seven major Axis operations specifically aimed at eliminating all or most Yugoslav Partisan resistance . These major offensives were typically combined efforts by the German Wehrmacht and SS , Italy , Chetniks , the Independent State of Croatia , the Serbian collaborationist government , Bulgaria , and Hungary . In the first half of 1943 two of these offensives came close to defeating the Partisans . They are known by their German code names Fall Weiss ( Plan White ) and Fall Schwarz ( Operation Black ) , as the Battle of Neretva and the Battle of Sutjeska after the rivers in the areas they were fought , or the Fourth and Fifth Enemy Offensive , respectively , according to former Yugoslav historiography . Former Yugoslav historiographers numbered the seven major Axis offensives as follows : Allied support shifts . Later in the conflict the Partisans were able to win the moral , as well as limited material support of the Western Allies , who until then had supported General Draža Mihailović ' s Chetnik Forces , but were finally convinced of their collaboration by many intelligence - gathering missions dispatched to both sides during the course of the war . To gather intelligence , agents of the Western Allies were infiltrated into both the Partisans and the Chetniks . The intelligence gathered by liaisons to the resistance groups was crucial to the success of supply missions and was the primary influence on Allied strategy in Yugoslavia . The search for intelligence ultimately resulted in the demise of the Chetniks and their eclipse by Tito ’ s Partisans . In 1942 , though supplies were limited , token support was sent equally to each . The new year would bring a change . The Germans were executing Operation Schwarz ( Battle of Sutjeska , the Fifth anti - Partisan offensive ) , one of a series of offensives aimed at the resistance fighters , when F . W . D . Deakin was sent by the British to gather information . His reports contained two important observations . The first was that the Partisans were courageous and aggressive in battling the German 1st Mountain and 104th Light Division , had suffered significant casualties , and required support . The second observation was that the entire German 1st Mountain Division had transited from USSR on rail lines through Chetnik - controlled territory . British intercepts ( ULTRA ) of German message traffic confirmed Chetnik timidity . Even though today many circumstances , facts , and motivations remain unclear , intelligence reports resulted in increased Allied interest in Yugoslavia air operations and shifted policy . In September 1943 , at Churchill ’ s request , Brigadier General Fitzroy Maclean was parachuted to Tito ’ s headquarters near Drvar to serve as a permanent , formal liaison to the Partisans . While the Chetniks were still occasionally supplied , the Partisans received the bulk of all future support . Thus , after the Tehran Conference the Partisans received official recognition as the legitimate national liberation force by the Allies , who subsequently set - up the RAF Balkan Air Force ( under the suggestion of Brigadier - General Fitzroy Maclean ) with the aim to provide increased supplies and tactical air support for Marshal Tito ' s Partisan forces . Allied aircraft specifically started targeting ZNDH ( Air Force of the Independent State of Croatia ) and Luftwaffe bases and aircraft for the first time as a result of the Seventh anti - Partisan Offensive , including " Operation Rösselsprung " in late May 1944 . Up until then Axis aircraft could fly inland almost at will as long as they remained at low altitude . Yugoslav Partisan units on the ground frequently complained about enemy aircraft attacking them while hundreds of Allied aircraft flew above at higher altitude . This changed during " Rösselsprung " as Allied fighter - bombers went low en - masse for the first time , establishing full aerial superiority . Consequently , both the ZNDH and Luftwaffe were forced to limit their operations in clear weather to early morning and late afternoon hours . In January 1944 , Tito ' s forces unsuccessfully attacked Banja Luka . But , while Tito was forced to withdraw , Mihajlović and his forces were also noted by the Western press for their lack of activity . On 16 June 1944 , the Tito - Šubašić agreement between the Partisans and the Yugoslavian Government in exile of King Peter II was signed on the island of Vis . This agreement was an attempt to form a new Yugoslav government which would include both the communists and the royalists . It called for a merge of the Partisan Anti - Fascist Council of National Liberation of Yugoslavia ( " Antifašističko V ( ij ) eće Narodnog Oslobođenja Jugoslavije " , AVNOJ ) and the Government in exile . The Tito - Šubašić agreement also called on all Slovenes , Croats , and Serbs to join the Partisans . The Partisans were recognized by the Royal Government as Yugoslavia ' s regular army . Mihajlović and many Chetniks refused to answer the call . Between 30 March and 8 April 1945 , General Mihailović ' s Chetniks mounted a final attempt to establish themselves as a credible force fighting the Axis in Yugoslavia . The Chetniks under Lieutenant Colonel Pavle Đurišić fought a combination of Ustaša and Croatian Home Guard forces in the Battle on Lijevča field . In late March 1945 elite NDH Army units were withdrawn from the Srem front to destroy Djurisic ’ s Chetniks trying to make their way across the northern NDH . The battle was fought near Banja Luka in what was then the Independent State of Croatia and ended in a decisive victory for the Independent State of Croatia forces . Macedonia . On 19 April 1941 , Bulgaria occupied Macedonia and some districts of Eastern Serbia , which , with Western Thrace and Eastern Greek Macedonia ( the Aegean Province ) , were annexed by Bulgaria on 14 May . On 15 January 1942 , the Bulgarian 1st Army of 3 infantry divisions transferred to South - East Serbia . Headquartered at Niš , it replaced German divisions needed in Croatia and USSR . On 7 January 1943 , it also occupied South - West Serbia . Savage pacification measures reduced Partisan activity appreciably . Bulgarian infantry divisions participated in the Fifth anti - Partisan Offensive as a blocking force of the Partisan escape - route from Montenegro into Serbia and in the Sixth anti - Partisan Offensive in Eastern Bosnia . On 10 September 1944 , Bulgaria changed sides and declared war on Germany as an Allied Power . The Germans swiftly disarmed the 1st Occupation Corps of 5 divisions and the 5th Army , despite heroic but short - lived resistance by the latter . Survivors retreated to Bulgaria , joining the new 450 , 000 - strong Bulgarian National Armed Forces . On 8 October , the 1st and 4th Armies occupied Vardar Macedonia with Partisan permission . The 2nd Army then occupied South - Eastern Serbia . The 1st Army then swung north with the Soviet 3rd Ukrainian Front , through Eastern Yugoslavia and South - Western Hungary , before linking up with the British 8th Army in Austria in May 1945 . Italy Surrenders . The Italian High Command assigned 24 divisions and three coastal brigades to occupation duties in Yugoslavia from 1941 . These units were located from Slovenia , Croatia and Dalmatia through to Montenegro and Kosovo . On 8 September 1943 , the Italians concluded an armistice with the Allies , leaving 17 divisions stranded in Yugoslavia . All divisional commanders refused to join the Germans . Two Italian infantry divisions joined the Montenegrin Partisans as complete units , whilst another joined the Albanian Partisans . Other units surrendered to the Germans , to face imprisonment in Germany or summary execution . Others surrendered themselves , arms , ammunition and equipment to Croatian forces or to the Partisans , simply disintegrated , or reached Italy on foot via Trieste or by ship across the Adriatic . The Italian Governorship of Dalmatia was disestablished and the country ' s possessions were subsequently divided between Germany which established its Operational Zone of the Adriatic Littoral and the Independent State of Croatia which established the new district of Sidraga - Ravni Kotari . Allied offensive in the Balkans . In August 1944 , King Michael I of Romania staged a coup , Romania quit the war , and the Romanian army was placed under the command of the Red Army . Romanian forces , fighting against Germany , participated in the Prague Offensive . Bulgaria quit as well and , on 10 September , declared war on Germany and its remaining allies . The weak divisions sent by the Axis powers to invade Bulgaria were easily driven back . In Macedonia , the Bulgarian troops , surrounded by German forces and betrayed by high - ranking military commanders , fought their way back to the old borders of Bulgaria . Three Bulgarian armies ( some 455 , 000 strong in total lead by Georgi Marinov Mandjev from the village of Goliamo Sharkovo – Elhovo ) entered Yugoslavia in late September 1944 with the prearranged consent of Tito and the Partisans and moved from Sofia to Niš and Skopje with the strategic task of blocking the German forces withdrawing from Greece . Southern and eastern Serbia and Macedonia were liberated within two months and the 130 , 000 - strong Bulgarian First Army continued to Hungary . Concurrently , with Allied air support and assistance from the Red Army , the Partisans turned their attention to the Serbian Military Administration , the state of the Serbian Axis fifth column . The area under its had seen relatively little fighting since the fall of the " Republic of Užice " in 1941 ( see First anti - Partisan offensive ) . In September , the Red Army and the Partisans launched the Belgrade Offensive , and took the city on 20 October . At the onset of winter , the Partisans effectively controlled the entire eastern half of Yugoslavia — Serbia , Macedonia , Montenegro — as well as most of the Dalmatian coast . The Wehrmacht and the forces of the Ustaše - controlled Independent State of Croatia fortified a front in Syrmia that held through the winter of 1944 – 45 in order to aid the evacuation of German troops from Greece . To raise the number of Partisan troops Tito declared a general amnesty for all members of quisling forces that switched sides before 31 December 1944 . Partisan General Offensive . The Germans continued their retreat relatively undisturbed . Having lost the easier withdrawal route through Serbia , they fought to hold the Srem front in order to secure the more difficult passage through Kosovo , Sandzak and Bosnia . They even scored a series of temporary successes against the People ’ s Liberation Army . They left Mostar on 22 February 1945 . They did not leave Sarajevo until 15 April . Sarajevo had assumed a last - moment strategic position as the only remaining withdrawal route and was held at substantial cost . In early March the Germans moved troops from southern Bosnia to support an unsuccessful counter - offensive in Hungary , which enabled the NOV to score some successes by attacking the Germans ’ weakened positions . Although strengthened by Allied aid , a secure rear and mass conscription in areas under their control , the one - time partisans found it difficult to switch to conventional warfare , particularly in the open country west of Belgrade , where the Germans held their own until mid - April in spite of all of the raw and untrained conscripts the NOV hurled in a bloody war of attrition against the Srem Front . On 20 March 1945 , the Partisans launched a general offensive in the Mostar - Višegrad - Drina sector . With large swaths of Bosnian , Croatian and Slovenian countryside already under Partisan guerrilla control , the final operations consisted in connecting these territories and capturing major cities and roads . For the general offensive Marshal Josip Broz Tito commanded a Partisan force of about 800 , 000 men organized into four armies : the 1st Army commanded by Peko Dapčević , 2nd Army commanded by Koča Popović , 3rd Army commanded by Kosta Nađ , and the 4th Army commanded by Petar Drapšin . In addition , the Yugoslav Partisans had eight independent army corps ( the 2nd , 3rd , 4th , 5th , 6th , 7th , 9th , and the 10th ) . Set against the Yugoslav Partisans was German General Alexander Löhr of Army Group E ( " Heeresgruppe E " ) . This Army Group had seven army corps ( the XV Mountain , XV Cossack , XXI Mountain , XXXIV , LXIX , and LXXXXVII ) . These corps included seventeen weakened divisions ( 1st Cossack , 2nd Cossack , 7th SS , 11th Luftwaffe Field , 22nd , 41st , 104th , 117th , 138th , 181st , 188th , 237th , 297th , 369th Croat , 373rd Croat , 392nd Croat and the 14th SS Ukrainian Division ) . In addition to the seven corps , the Axis had remnant naval and Luftwaffe forces , under constant attack by the British Royal Navy , Royal Air Force and United States Air Force . The Army of the Independent State of Croatia was reorganized in November 1944 to combine the units of the Ustaše and Croatian Home Guard into eighteen divisions , comprising 13 infantry , two mountain , two assault and one replacement Croatian Divisions , each with its own organic artillery and other support units . There were also several armoured units . From early 1945 , the Croatian Divisions were allocated to various German Corps and by March 1945 were holding the Southern Front . Securing the rear areas were some 32 , 000 men of the Croatian Gendarmerie ( " Hrvatsko Oruznistvo " ) , organised into 5 Police Volunteer Regiments plus 15 independent battalions , equipped with standard light infantry weapons , including mortars . The Air Force of the Independent State of Croatia ( " Zrakoplovstvo Nezavisne Države Hrvatske " , or ZNDH ) and the units of the Croatian Air Force Legion ( " Hrvatska Zrakoplovna Legija " , or HZL ) , returned from service on the Eastern Front provided some level of air support ( attack , fighter and transport ) right up until May 1945 , encountering and sometimes defeating opposing aircraft from the British Royal Air Force , United States Air Force and the Soviet Air Force . Although 1944 had been a catastrophic year for the ZNDH , with aircraft losses amounting to 234 , primarily on the ground , it entered 1945 with 196 machines . Further deliveries of new aircraft from Germany continued in the early months of 1945 to replace losses . By 10 March , the ZNDH had 23 Messerschmitt 109 G & Ks , three Morane - Saulnier M . S . 406 , six Fiat G . 50 , and two Messerschmitt 110 G fighters . The final deliveries of up - to - date German Messerschmitt 109 G and K fighter aircraft were still taking place in March 1945 . and the ZNDH still had 176 aircraft on its strength in April 1945 . Serbian units included the remnants of the Serbian State Guard and the Serbian Volunteer Corps from the Serbian Military Administration . There were even some units of the Slovene Home Guard ( " Slovensko domobranstvo " , or SD ) still intact in Slovenia . By the end of March , 1945 , it was obvious to the Croatian Army Command that , although the front remained intact , they would eventually be defeated by sheer lack of ammunition . For this reason , the decision was made to retreat into Austria , in order to surrender to the British forces advancing north from Italy . The German Army was in the process of disintegration and the supply system lay in ruins . Bihać was liberated by the Partisans the same day that the general offensive was launched . The 4th Army , under the command of Petar Drapšin , broke through the defenses of the XVth SS Cossack Cavalry Corps . By 20 April , Drapšin liberated Lika and the Croatian Littoral , including the islands , and reached the old Yugoslav border with Italy . On 1 May , after capturing the former Italian possessions of Rijeka and Istria from the German LXXXXVII Corps , the Yugoslav 4th Army beat the western Allies to Trieste by one day . The Yugoslav 2nd Army , under the command of Koča Popović , forced a crossing of the Bosna River on 5 April , capturing Doboj , and reached the Una River . On 6 April , the 2nd , 3rd , and 5th Corps of the Yugoslav Partisans took Sarajevo from the German XXI Corps . On 12 April , the Yugoslav 3rd Army , under the command of Kosta Nađ , forced a crossing of the Drava river . The 3rd Army then fanned out through Podravina , reached a point north of Zagreb , and crossed the old Austrian border with Yugoslavia in the Dravograd sector . The 3rd Army closed the ring around the enemy forces when its advanced motorized detachments linked up with detachments of the 4th Army in Carinthia . Also , on 12 April , the Yugoslav 1st Army , under the command of Peko Dapčević penetrated the fortified front of the German XXXIV Corps in Syrmia . By 22 April , the 1st Army had smashed the fortifications and was advancing towards Zagreb . The long - drawn out liberation of western Yugoslavia caused more victims among the population . The breakthrough of the Srem front on 12 April was , in Milovan Dilas ’ s words , “ the greatest and bloodiest battle our army had ever fought ” , and it would not have been possible had it not been for Soviet instructors and arms . By the time General Peko Dapčević ’ s NOV units had reached Zagreb , on 9 May 1945 , they had perhaps lost as many as 36 , 000 dead . There were by then over 400 , 000 refugees in Zagreb . After entering Zagreb with the Yugoslav 2nd Army , both armies advanced in Slovenia . Final operations . On 2 May , the German capital city , Berlin , fell to the Red Army . On 8 May 1945 , the Germans surrendered unconditionally and the war in Europe officially ended . The Italians had quit the war in 1943 , the Bulgarians in 1944 , and the Hungarians earlier in 1945 . Despite the German capitulation , however , sporadic fighting still took place in Yugoslavia . On 7 May , Zagreb was evacuated , on 9 May , Maribor and Ljubljana were captured by the Partisans , and General Alexander Löhr , Commander - in - Chief of Army Group E was forced to sign the total surrender of the forces under his command at Topolšica , near Velenje , Slovenia , on Wednesday 9 May 1945 . Only the Croatian and other anti - Partisan forces remained . From 10 to 15 May , the Yugoslav Partisans continued to face resistance from Croatian , and other anti - Partisan forces throughout the rest of Croatia and Slovenia . The Battle of Poljana , the last battle of World War II in Europe , started on 14 May , ending on 15 May 1945 at Poljana , near Prevalje in Slovenia . It was the culmination and last of a series of battles between Yugoslav Partisans and a large ( in excess of 30 , 000 ) mixed column of German Army ( " Wehrmacht Heer " ) soldiers together with Croatian Ustaše , Croatian Home Guard ( " Hrvatsko Domobranstvo " ) , Slovenian Home Guard ( " Domobranci " ) , and other anti - Partisan forces who were attempting to retreat to Austria . Aftermath . On 15 May 1945 the Croatian Home Guard , the Ustaše , the XVth SS Cossack Cavalry Corps and the remnants of the Serbian State Guard , and the Serbian Volunteer Corps , surrendered to British forces . The Croatians attempted to negotiate a surrender to the British under the terms of the Geneva Convention , but were ignored . The Independent State of Croatia had joined that Convention on 20 January 1943 , and was recognised by it as a " belligerent " , that is , as a national state with armed forces in the field . All the signatories of the Convention , including Great Britain and the United States , were informed that this recognition had been given . On 5 May , in the town of Palmanova ( 50 km northwest of Trieste ) , between 2 , 400 and 2 , 800 members of the Serbian Volunteer Corps surrendered to the British . On 12 May , about 2 , 500 additional Serbian Volunteer Corps members surrendered to the British at Unterbergen on the Drava River . On 11 and 12 May , British troops in Klagenfurt , Austria , were harassed by arriving forces of the Yugoslav Partisans . In Belgrade , the British ambassador to the Yugoslav coalition government handed Tito a note demanding that the Yugoslav troops withdraw from Austria . On 15 May , Tito placed Partisan forces in Austria under Allied control . A few days later he agreed to withdraw them . By 20 May , Yugoslav troops in Austria had begun to withdraw . Around 1 June , most of the Serbian State Guard , the Serbian Volunteer Corps , the Croatian Home Guard , the Ustaše , and the XVth SS Cossack Cavalry Corps who surrendered to the British were turned over to the Yugoslav government as part of what is sometimes referred to as Operation Keelhaul . The Partisans proceeded to brutalize the POW s in what became known as the Bleiburg massacre s . On 8 June , the United States , the United Kingdom , and Yugoslavia agreed on the control of Trieste . On 8 March 1945 , a coalition Yugoslav government was formed in Belgrade with Tito as Premier and Ivan Šubašić as Foreign Minister . King Peter II of Yugoslavia agreed not to return until after an election can be organized . On 29 November , in accordance with overwhelming election results , Peter II was deposed by Yugoslavia ' s Constituent Assembly . On the same day , the Federal People ' s Republic of Yugoslavia was established as a socialist state during the first meeting of the Yugoslav Parliament in Belgrade . Josip Broz Tito was appointed Prime Minister . On 13 March 1946 , Mihailović was captured by agents of the Yugoslav Department of National Security ( " Odsjek Zaštite Naroda " or OZNA ) . From 10 June to 15 July of the same year , he was tried for high treason and war crimes . On 15 July , he was found guilty and sentenced to death by firing squad . On 16 July , a clemency appeal was rejected by the Presidium of the National Assembly . During the early hours of 18 July , Mihailović , together with nine other Chetnik officers , was executed in Lisičiji Potok . This execution essentially ended the World War II - era civil war between the communist Partisans and the royalist Chetniks . Casualties . Yugoslav casualties . The Yugoslav government estimated the number of casualties to be at 1 , 704 , 000 and submitted the figure to the International Reparations Commission in 1946 without any documentation . The figure included war related deaths but also the expected population if war did not break out , the number of unborn children , and losses from emigration and disease . The same figure was later submitted to the Allied Reparations Committee in 1948 but was claimed to be only from war related deaths . After Germany requested verifiable data the Yugoslav Federal Bureau of Statistics created a nationwide survey in 1964 . The total number of those killed was found to be 597 , 323 . The list stayed a state secret until 1989 when it was published for the first time . The U . S . Bureau of the Census published a report in 1954 that concluded that Yugoslav war related deaths were 1 , 067 , 000 . The U . S . Bureau of the Census noted that the official Yugoslav government figure of 1 . 7 million war dead was overstated because it " was released soon after the war and was estimated without the benefit of a postwar census " . A recent study by Vladimir Žerjavić estimates total war related deaths at 1 , 027 , 000 . Military losses of 237 , 000 Yugoslav partisans and 209 , 000 Croatian Home Guard and Ustase . Civilian dead of 581 , 000 , including 57 , 000 Jews . Losses of the Yugoslav Republics were Bosnia 316 , 000 ; Serbia 273 , 000 ; Croatia 271 , 000 ; Slovenia 33 , 000 ; Montenegro 27 , 000 ; Macedonia 17 , 000 ; and killed abroad 80 , 000 . Bogoljub Kočović a statistician , who is a Bosnian Serb by ethnic affiliation , calculated that the actual war losses were 1 , 014 , 000 . The late Jozo Tomasevich , Professor Emeritus of Economics at San Francisco State University , believes that the calculations of Kočović and Žerjavić “ seem to be free of bias , we can accept them as reliable ” . The reasons for the high human toll in Yugoslavia were as follows : In Slovenia , the Institute for Contemporary History , Ljubljana launched a comprehensive research on the exact number of victims of World War II in Slovenia in 1995 . After more than a decade of research , the final report was published in 2005 , which included a list of names . The number of victims was set at 89 , 404 . The figure also includes the victims of summary killings by the Communist regime immediately after the war ( around 13 , 500 people ) . The results of the research came as a shock for the public , since the actual figures were more than 30 % higher than the highest estimates during the Yugoslav period . Even if one counts only the number of deaths up to May 1945 ( thus excluding the military prisoners killed by the Yugoslav Army between May and July 1945 ) , the number remains considerable higher than the highest previous estimates ( around 75 , 000 deaths vs . an estimate of 60 , 000 ) . There are several reasons for such a difference . The new comprehensive research also included Slovenes killed by the Partisan resistance , both in battle ( members of collaborationist and anti - Communist units ) , and civilians ( around 4 , 000 between 1941 and 1945 ) . Furthermore , the new estimates includes all the Slovenians from Nazi - occupied Slovenia who were drafted in the Wehrmacht and died either in battle or in prisoner camps during the war . The figure also includes the Slovenes from the Julian March who died in the Italian Army ( 1940 – 1943 ) , those from Prekmurje who died in the Hungarian Army , and those who fought and died in various Allied ( mostly British ) units . The figure does not include victims from Venetian Slovenia ( except of those who joined the Slovenian Partisan units ) , nor does it include the victims among Carinthian Slovenes ( again with the exception of those fighting in the Partisan units ) and Hungarian Slovenes . 47 % percent of casualties during the war were partisans , 33 % were civilians ( of which 82 % were killed by Axis powers or Slovene home guard ) , and 20 % were members of the Slovene home guard . In Croatia , the Commission for the Identification of War and Post - War Victims of the Second World War was active from 1991 until the Seventh Government of the republic , under Prime Minister Ivica Račan ended the commission ' s work unfinished in 2002 . In the 2000s , concealed mass grave commissions were established in both Slovenia and Serbia to document and excavate mass graves from the Second World War . German casualties . According to German casualty lists quoted by The Times for July 30 , 1945 , from documents found amongst the personal effects of General Hermann Reinecke , head of the Public Relations Department of the German High Command , total German casualties in the Balkans amounted to 24 , 000 killed and 12 , 000 missing , no figure being mentioned for wounded . A majority of these casualties suffered in the Balkans were inflicted in Yugoslavia .