Vyborg – Petrozavodsk Offensive The Vyborg – Petrozavodsk Offensive or Karelian offensive was a strategic operation by the Soviet Leningrad and Karelian Front s against Finland on the Karelian Isthmus and East Karelia fronts of the Continuation War , on the Eastern Front of World War II . The Soviet forces captured East Karelia and Viborg . After that , however , the fighting reached a stalemate . The operations of the strategic offensive can be divided into the following offensives : Background . In January 1944 , Soviet forces raised the Siege of Leningrad and drove the German Army Group North to the Narva - Lake Ilmen - Pskov line . Finland asked for peace conditions in February , but the Parliament , Eduskunta considered the received terms impossible to fulfill . After Finland had rejected the peace conditions , and Germany denied the Soviets from the Baltic Sea at Narva , the Stavka ( Main Command of the Armed Forces of the Soviet Union ) started to prepare for an offensive to force Finland ' s exit from the war . The plan . In order to destroy the Finnish Army and to push Finland out of the war , the Stavka decided to conduct the Vyborg – Petrozavodsk Offensive . The strategy called for a two - pronged offensive , one from Leningrad via Viborg to the Kymi river , and the second across the Svir River through Petrozavodsk and Sortavala past the 1940 border , preparing for an advance deep into Finland . The plan called for the Finnish army to be destroyed on the Karelian Isthmus , and the remains blocked against the western shore of Lake Ladoga between the two assaults and Lake Saimaa . The main strategic objectives of the offensive were to push Finnish forces away from the north of Leningrad , to drive Finland out of the war , and to create better conditions for a major offensive to the south against Germany . The Finnish army had been preparing defensive fortifications since 1940 , and three lines of defence on the Karelian Isthmus . The first two were the " Main line " , which was constructed along the frontline of 1941 , and the VT - line ( Vammelsuu - Taipale ) running 20 km behind the main line . These lines were reinforced with numerous concrete fortifications , but the work was still ongoing . The third line , the VKT - line ( Viipuri - Kuparsaari - Taipale ) was still on the drawing board and the construction of the fortifications began in late May 1944 at the Viborg sector of the line . At the northern bank of the Svir River ( ) the Finnish army had prepared a defence in depth area which was fortified with strong - points with concrete pillbox es , barbed wire , obstacles and trenches . After the Winter War , the Salpa Line was built behind the 1940 border with concrete bunkers in front of the Kymi river . To overcome these obstacles , the Stavka assigned 11 divisions and 9 tank and assault gun regiments to the Leningrad Front . That meant that there were 19 divisions , 2 division strength fortified region s , 2 tank brigades , 14 tank and assault gun regiments at the Isthmus , all of which included over 220 artillery and rocket launcher batteries ( almost 3 , 000 guns / launchers ) . Around 1 , 500 planes from the 13th Air Army and the Baltic Fleet naval aviation also contributed to the operation which included surface and naval infantry units of the Baltic Fleet . To the east of Karelia , the Stavka planned to use 9 divisions , 2 sapper brigades , 2 tank brigades and 3 assault gun regiments , raising the whole strength to 16 divisions , 2 fortified regions , 5 separate rifle brigades , 2 tank brigades , 3 assault gun regiments and 3 tank battalions . They were supported by Lake Ladoga and Lake Onega naval flotilla s and the 7th Air Army . Vyborg Offensive . At the Karelian Isthmus front there were on average 120 Red Army artillery pieces for every kilometer , with up to 220 artillery pieces per kilometer on the breakthrough sector at Valkeasaari . In addition to heavy coastal artillery of the Leningrad area and the guns of the capital ships of the Baltic Fleet ( " Oktyabrskaya Revolutsiya " , , ) Stavka had also assigned heavy siege artillery ( 280 to 305 mm ) to support of the attack . On June 9 , a day before the main Soviet offensive , the 1 , 600 - strong 13th Air Army conducted a major aerial assault . At the same time , artillery units of the Leningrad Front and the Baltic Fleet shelled Finnish positions for 10 hours . The Finnish Army was in a well - fortified position , but the Soviet air attacks surprised the defending Finnish army and undermined its resistance causing many Finnish units to retreat and suffer from thousands of desertions . Valkeasaari . On June 10 , the Soviet 21st Army spearheaded by 30th Guards Corps opened the offensive on the Valkeasaari sector which was defended by of Finnish 10th Division . During the day , the Soviet units captured frontline trenches and destroyed fortifications , shattering the first Finnish defense line at the breakthrough sector . Kuuterselkä . On June 13 , the Soviet 21st Army ' s offensive reached the partially completed VT - line . The defensive position was breached at Kuuterselkä already on June 15 . Though the line was breached the Finnish resistance managed to delay further Soviet advances . Siiranmäki . Simultaneous to Kuuterselkä the Soviet 23rd Army attempted to break through at a perceived weak point in the Finnish VT - line at Siiranmäki . Siiranmäki was the first place where Finnish troops were able to use Panzerfaust s and Panzerschreck s imported from Germany . Though Finnish troops managed to contain the Soviet breakthrough at Siiranmäki it was not enough to keep the VT - line as Kuuterselkä had already been breached . Viborg . The Finnish army attempted to buy time by engaging in delaying action during retreat so that additional forces from East Karelia would be able to reach the front , and the VKT - line could be prepared for combat . However , on June 19 forces of the first Leningrad Front had reached Viborg , and the first phase of the offensive was completed by the capture of the city on June 20 , when the defending Finnish 20th Infantry Brigade fled in panic . Though Leningrad Front had managed to capture Viborg within the time table set by Stavka they had been unable to prevent retreating Finnish units from regrouping and fortifying on the VKT - line . Virojoki - Lappeenranta Offensive . Mannerheim had asked for German help , and on June 17 Gefechtsverband Kuhlmey arrived in Finland , followed on June 21 by the 303rd Assault Gun Brigade ( at half strength ) and the 122nd Infantry Division . Also , new German anti - tank weapons , " Panzerfaust s " and " Panzerschreck s " , were issued to Finnish army troops . Late on June 21 , German foreign minister von Ribbentrop arrived to Finland in an attempt to extract political concessions from the military help . On June 21 , Stavka ordered continued attacks on the Imatra - Lappeenranta - Virojoki defence line , on the Salpa Line sector of the front . Another group would attack northwards to Käkisalmi ( now Priozersk , Russia ) and surround the Finns defending the eastern VKT - line while preparations would be made for an advance towards Kotka , Kouvola and the Kymi river . On June 21 the Finnish government asked for Soviet peace terms . The response arrived on the next day and it demanded Finnish capitulation before any conditions could be presented . This created confusion in the Finnish government , where Ryti and Tanner were willing to repeat the inquiry about the conditions , while others opposed the capitulation . During the meeting Marshal Mannerheim was called , and he stated that the Soviet demand constituted an unconditional surrender . When Paasikivi ' s negotiation trip to Moscow in March 1944 , which was initiated by the Soviet ambassador in Stockholm , but turned out to be a Soviet dictation of terms , was remembered , the government decided to interpret the Soviet response as a demand for unconditional surrender . It seemed that after Finnish unwillingness to accept the Soviet proposals in April 1944 , owing to excessive reparation demands , Finland was to be offered only unconditional surrender . This was in line with Churchill ' s statement that as an Axis belligerent , Finland ' s surrender must be unconditional . The Soviet authorities denied this interpretation in an article published in Pravda on July 2 , 1944 , Furthermore , it is also known that at June 26 Stalin even told American ambassador Harriman that US diplomats could try to clarify to the Finns that he did not intend to take over the country . An unsigned draft document called " The Terms for Finnish Unconditional Surrender " was found in October 1993 in the Russian Foreign Ministry archive , which led some historians to conclude that unconditional surrender was indeed the Soviet goal . According to Baryshnikov this and similar drafts for the other countries the USSR was at war with existed since 1943 , and they were replaced by new ones in the summer of 1944 . With Finnish army reinforcements , there were 268 , 000 Finnish army troops with 2 , 350 guns , 110 tanks / assault guns and 250 planes facing the two Red Army Fronts ; 40 % of the men and guns , and all the tanks were on the Isthmus . In total , the Red Army had a 1 . 7 : 1 advantage in men , 5 . 2 : 1 advantage in guns , and 6 - 7 : 1 advantage in planes and tanks against the Finnish army . The offensive continued on June 25 , when the Red Army breached the VKT - line at Tali , between the Viborg Bay and the Vuoksi river . On June 26 the Finnish president Ryti gave the guarantee to Ribbentrop that Finland would fight to the end alongside with Germany . When it became evident that a breakthrough was not possible at Ihantala , the Leningrad Front attempted to double envelope the defenders with the twin assaults at the Viborg Bay and Vuosalmi . However , the Finnish army was able to hold its positions on these sectors of the front . On July 12 Stavka ordered Leningrad front to release offensive elements from the Finnish front , and on July 15 , the Red Army troops were ordered to assume a defensive posture , and offensive elements ( mostly armor ) were transferred to the German front for use in Operation Bagration . Koivisto Landing Operation . After Soviet offensive on the Karelian Isthmus pushed north past Koivisto the Finnish forces defending the islands became isolated . After Soviet 21st Army failed to attack the islands the Leningrad front ordered the offensive to Soviet Baltic Fleet to capture the islands . The initial Soviet landing was contained but the Finnish Navy soon evacuated the defending forces . This movement was largely unopposed . Although the eagerness of the commanders to evacuate preserved the defending forces , the loss of the islands proved costly because the Soviet Baltic Fleet gained a safe route to the Viborg Bay . Tienhaara . After capturing Viborg the lead elements of the Soviet 21st Army attempted to push forward along the main road leading north from Viborg but strong artillery support , narrow area of operations , and very favorable terrain made it possible for the Finnish to hold Soviet advance forcing the Soviet 21st Army to find a more suitable location for breaching the Finnish VKT - line . Tali - Ihantala . After Soviet 21st Army easily cleared the defending Finnish troops from Viborg on June 20 , the Soviet forces attempted to press on the offensive , but met stubborn Finnish resistance at Tali and were forced to stop . After bringing fresh troops to the front the 21st Army managed to push Finnish lines to Ihantala but failed to create any breakthroughs . The battle fought over the area is considered to be the largest battle in the Nordic countries history . The Soviet 23rd Army joined the offensive by attempting to break through the Finnish lines between Tali and Vuoksi towards Noskua but the repeated Soviet attacks were halted by the highly efficient Finnish artillery . In the end the battle of Tali - Ihantala was a defensive strategic victory for the Finnish army . It blocked the possibility for the Soviet army to break through to the Finnish heartland and the road to Helsinki . Viborg Bay . After the initial efforts of the 21st Army in Tali - Ihantala did not produce a breakthrough , the Leningrad Front ordered the 59th Army to capture the islands dominating the Viborg Bay and perform an amphibious landing on the opposing shore . Though the landings on the islands were ultimately successful , the attempted crossing failed . Vuosalmi . As the 21st Army was unable to advance , the Soviet 23rd Army attempted a crossing in the Vuosalmi region of the Vuoksi waterway . Though Soviet forces successfully pushed Finnish troops from Äyräpää ridge dominating the crossing and managed to create a strong bridgehead on the opposing side , the defending Finnish troops were able to contain it . Svir – Petrozavodsk Offensive . Soviet Union ' s Karelian Front started offensive in the Olonets and White Karelia on June 20 . Weakened Finnish forces proved unable to stop the offensive which reached Olonets on June 25 , and on June 29 , took Petrozavodsk , one of the main goals of the operation . Long advance after the delaying Finnish forces sapped the Soviet strength and the main push of the 7th Army stopped at Finnish U - line . The Soviet 7th Army and the 32nd Army tried to go around the U - line attacking further to the north but failed to break through the defending Finnish units in battles fought in the wilderness of Karelia . The last attempt to resume the offensive was made further north by two divisions of the Soviet 32nd Army which were defeated by counterattacking Finns in the battle of Ilomantsi . Svir . The Finnish Army had previously withdrawn most of its forces from the southern shore of the Svir River , so when the Red Army offensive started on 21 June , it did not achieve the desired surprise . The Karelian Front ' s Soviet 7th Army - 37th Guards , 4th and 99th Corps - crossed the river using amphibious vehicles on the following day and secured a bridgehead 8 km deep and 16 km wide . After securing the crossing the Soviet forces continued to chase the withdrawing Finns towards defenses of the ' PSS ' - line . Tuloksa landing operation . On June 23 , 70th naval infantry brigade attacked and captured a beachhead behind the Finnish lines and also beyond the ' PSS ' - line between the Viteleenjoki and Tuuloksenjoki rivers , severing the main road and railroad connections along the shore of Lake Ladoga . As Finns had previously moved most of the coastal defenses to the Karelian Isthmus the Soviet landing met only skeleton defense . Finnish attempts to drive the Soviets into the Ladoga proved unsuccessful but it had pushed the defending Soviets to the difficult position as ammunition and supplies started running low . Situation in the beachhead was improved when the 3rd Naval Infantry Brigade started its landings on the evening of June 24 . Bad weather hampered the efforts the brigade was finally unloaded on the June 26 and it was able to link up with the advancing 7th Army . Landing caused some trouble for the defending Finns as it cut the railroad line running along the coast of lake Ladoga . Cutting of the road was of less consequence as Finns had already previously constructed new parallel road further inland in fear of landing however the heavy traffic of the withdrawing forces totally ruined the new road forcing some of the equipment to be abandoned . Though Finns managed to withdraw to the new defensive line the advancing Soviet units broke through the new line at Vitele already on June 28 forcing Finns to continue delaying the advancing Soviets while withdrawing towards ' U ' - line . Nietjärvi . The Finnish Army retreated further , delaying the Karelian Front advance , allowing for the U - line , running northwards from Pitkäranta to Loimola and Kivijärvi , to be reinforced . The first Karelian Front 7th Army ' s units reached the U - line on July 10 , but were fatigued following the long offensive , and failed to breach the defence line . Soviet attempts to break through the U - line at Nietjärvi ended with clear Soviet failure on July 17 when Finnish counterattack regained the lost positions on the U - line causing severe losses to the Soviet 114th Division . Once the attempts to gain breakthrough into the Finnish U - line had failed Red Army attempted to go around the line by flanking it through the frontier north of the line . As Finns countered the flanking maneuvers the fighting extended far into the frontier in a makeshift extension of the U - line however Soviet 7th Army managed neither to flank the extending Finnish line nor to break through it . Ilomantsi . North of the U - line the Soviet 32nd Army which consisted of 176th , 289th , 313th and 368th Rifle Divisions advanced after capturing Petrozavodsk towards small Finnish town of Ilomantsi while being delayed by defending Finnish 21st Brigade . Lack of suitable roads and the slow progress of 7th Army forced 32nd Army to move 313th and 368th Rifle Divisions to support 7th Army ' s offensive but they were blocked by the Finnish 1st Division . The Soviet attack towards Ilomantsi with the remaining 2 divisions ( 176th and 289th ) was initially successful , and the divisions reached the border of 1940 on July 21 , ( the only Soviet units which did so in the offensive ) , but in the ensuing battle the divisions were surrounded and forced to escape the encirclement suffering heavy losses and being forced to leave their artillery and other heavy equipment behind . Aftermath . The offensive succeeded in reclaiming East Karelia and driving the Finnish army to the northern side of the Viborg Bay and the Vuoksi River . It also reopened the original route of the Murman Railway and the White Sea Canal to the Karelian Front forces . However , the offensive failed to breach the VKT - line and reach the Kymi River as ordered by the Stavka . Despite the losses suffered , the Finnish army managed to avoid encirclements of units larger than a battalion in size . and benefited from supplies delivered by Germany . The psychological effect of the offensive on the Finnish leadership should not be underestimated . Even though the Finns had stopped the offensive at the Karelian Isthmus after 100 km and the Battle of Ilomantsi had shown that the Finnish army was still a viable fighting force , it was estimated that should the Soviet offensive continue at its full strength , the Finnish army would be able to last for three months at most . Though Soviet pressure against the Finns had relented and offensive troops were being moved to face the Germans , the Finns believed it would be possible for the Soviets to launch another major attack with only a few weeks of preparations . For Finland the overall situation required peace . During the height of the offensive in June 1944 , the Finns asked for negotiations and the Soviets responded with a demand for surrender , which in Finland was interpreted as an ambiguous demand for unconditional surrender and rejected . After the fighting had reached a stalemate in August 1944 , another attempt to seek peace was made by Finland . In September 1944 the Soviets offered peace terms that were roughly the same as in April 1944 , though some of the demands , which had been seen by the Finns as impossible to concede to , were reduced . The $ 600 million war reparations were halved and the time to pay them off was extended . This was probably in part brought about by international pressure exerted on the Soviets , especially by the U . S . and Britain . However , after the ceasefire the Soviets demanded that payments be based on 1938 prices which nearly doubled the actual amount to be paid , and so the Finns complained that the Soviets only pretended to lower the reparations . Despite not achieving all of the goals set by the Stavka , the offensive forced Finland from the war and to accept Soviet peace terms , or at least it was an important factor leading to the ceasefire negotiations that were resumed a month after the offensive had ended .