Operation Whirlwind Operation Whirlwind ( in Croatian : " Operacija Vihor " ) was a failed Croatian Army ( HV ) offensive in the Banovina region of Croatia , fought from 11 – 13 December 1991 , during the early stages of the Croatian War of Independence . The offensive employed a single infantry brigade as the main attacking force , supported by a bridging unit and a handful of tanks and armoured personnel carrier s . Even though the offensive met hardly any resistance in its initial stage , achieving tactical surprise , the operation was poorly planned , supported and executed , as a result of limited training and combat experience . The offensive established a short - lived bridgehead , evacuated in panic days after the operation commenced , under tank and mortar fire from the Yugoslav People ' s Army ( JNA ) deployed north of Glina . The operation was criticised for its poor planning and execution , insufficient preparation , reconnaissance and training , and inappropriate command and control methods applied by the Sisak Operational Group in charge of the offensive . It also lacked clear objectives . Afterwards , Croatian military authorities investigated the offensive , but found that there was very little written documentation , including written unit - level orders , pertaining to the operation . That led Admiral Davor Domazet - Lošo to conclude that the offensive was not formally authorised . The formal investigation did not specifically charge anyone with the failures , simply specifying the problems observed instead . Background . In 1990 , following the electoral defeat of the government of the Socialist Republic of Croatia , ethnic tensions worsened . The Yugoslav People ' s Army ( " Jugoslovenska Narodna Armija " – JNA ) confiscated Croatia ' s Territorial Defence ( " Teritorijalna obrana " - TO ) weapons to minimize resistance . On 17 August , the tensions escalated into an open revolt by Croatian Serbs , centred on the predominantly Serb - populated areas of the Dalmatian hinterland around Knin , parts of the Lika , Kordun , Banovina and eastern Croatia . This was followed by two unsuccessful attempts by Serbia , supported by Montenegro and Serbia ' s provinces of Vojvodina and Kosovo to obtain the Yugoslav Presidency ' s approval for a JNA operation to disarm Croatian security forces in January 1991 . After a bloodless skirmish between Serb insurgents and Croatian special police in March , the JNA itself , supported by Serbia and its allies , asked the Federal Presidency to give it wartime authorities and declare a state of emergency . The request was denied on 15 March , and the JNA came under the control of Serbian President Slobodan Milošević . Milošević , preferring a campaign to expand Serbia rather than to preserve Yugoslavia , publicly threatened to replace the JNA with a Serbian army and declared that he no longer recognized the authority of the Federal Presidency . By the end of the month , the conflict had escalated into the Croatian War of Independence . The JNA stepped in , increasingly supporting the Croatian Serb insurgents , and preventing Croatian police from intervening . In early April , the leaders of the Croatian Serb revolt declared their intention to integrate the area under their control , known as SAO Krajina , with Serbia . The Government of Croatia viewed this declaration as an attempt to secede . In May , the Croatian government responded by forming the Croatian National Guard ( " Zbor narodne garde " - ZNG ) , but its development was hampered by a United Nations ( UN ) arms embargo introduced in September . On 8 October , Croatia declared independence from Yugoslavia , and a month later the ZNG was renamed the Croatian Army ( " Hrvatska vojska " - HV ) . Late 1991 saw the fiercest fighting of the war , as the 1991 Yugoslav campaign in Croatia culminated in the Siege of Dubrovnik , and the Battle of Vukovar . In the western Slavonia , the HV managed to push back the JNA at several points , and secure Papuk Mountain in early December in Operation Otkos 10 . Order of battle . The principal force committed to the offensive , planned by the HV Sisak Operational Group ( OG ) , was the 102nd Infantry Brigade , attached to the Sisak OG by the Zagreb Operational Zone command , as the single combat unit deployed as a reserve in the Sisak OG area of responsibility ( AOR ) . Besides the 102nd Brigade , commanded by Captain Franc Ferenčak , the Zagreb Operational Zone deployed an armoured - mechanised unit attached directly to the Zagreb Operational Zone into the Sisak OG AOR . The unit consisted of eight tanks and two armoured personnel carrier s . The Sisak OG assigned the 10th Brigade of the Croatian TO to support the right flank of the 102nd Infantry Brigade , and the 2nd Battalion of the 2nd Guards Brigade , protecting the left flank of the 102nd Infantry Brigade , itself supported by the 2nd Battalion of the 144th Infantry Brigade . The Sisak OG assigned the Glina Battalion to reinforce the 102nd Infantry Brigade and the independent armoured - mechanised unit , attaching ten soldiers from the Glina Battalion to each battalion of the 10th and the 102nd brigades and two soldiers to each tank to serve as guides . In addition the Glina Battalion was tasked with reconnaissance , harassment of JNA ' s rear and securing captured infrastructure . Sisak special police was assigned to support the Glina Battalion , and indirectly the main offensive force , while the 36th Engineering - Pontoon Battalion was tasked with facilitating the Kupa River crossing by the 102nd Infantry Brigade . The Sisak OG was commanded by Major General Božo Budimir . The Croatian Serb TO and JNA defences immediately west of the city of Sisak and north of Glina were positioned along the right ( southern ) bank of the Kupa River , largely consisting of the JNA 592nd and the 622nd Mechanised Brigades . On the opposite bank , the HV 100th Infantry Brigade held positions west of Sisak , flanked by the 145th Infantry Brigade to its right , and the 10th brigade of the Croatian TO further to the west . The planned main axis of the Operation Whirlwind extended across the 592nd Mechanised Brigade AOR , commanded by Colonel Boško Džombić . Timeline . The HV 102nd Infantry Brigade arrived to the Sisak OG AOR on 11 December 1992 , and it was issued an order to undertake the offensive the same evening , at about 20 : 00 , leaving no time for any preparation or reconnaissance . A reconnaissance – sabotage detachment of the HV Glina Battalion and the special police force was ferried across the Kupa River on the night of 11 / 12 December , capturing the village of Stankovac and preparing to support the 102nd Infantry Brigade when it crosses the river . The 36th Engineering - Pontoon Battalion completed a crossing point in the village of Šišinec by 4 : 00 , and the lead elements of the 102nd Infantry Brigade crossed the Kupa River a half an hour later . The river crossing was unopposed until 08 : 00 , when the defending force launched a mortar attack against the crossing point . Nonetheless , the 1st Battalion of the 102nd Infantry Brigade cleared the river by 09 : 00 that morning and reached Stankovac . The independent armoured - mechanised unit crossed the Kupa River for three hours , completing the crossing at 13 : 00 , and headed south to Mala Solina , away . The unit was intercepted by JNA armour and it had to turn back to Stankovac . The situation was further complicated for the HV as the 10th Brigade did not even start to move south , while the 2nd Battalion of the 102nd Independent Brigade would not cross Kupa before its commander joined the unit at 16 : 00 . The 3rd Battalion of the 102nd Infantry Brigade reached the village of Vratečko on the right ( southern ) bank of the Kupa River , but it did not join the rest of the force south of Kupa because a bridge spanning the Glina River , separating the battalion from the rest of the brigade , remained out of HV ' s control . By the evening , the 2nd Battalion was ordered to separate from the main axis of the offensive and protect the right flank of the 1st Battalion of the 102nd Brigade — performing the task originally assigned to the 10th Brigade of the Croatian TO . At the same time , the 10th Brigade commanding officer was relieved of duty for failure to advance . Regardless , the unit remained inactive . The HV units that managed to cross the river on 12 December surprised the JNA and reported inflicting considerable casualties . On the night of 12 / 13 December , the air temperature dropped to , and HV troops sought shelter in Stankovac until the morning — shrinking the bridgehead held by the 102nd Infantry Brigade . In addition , the 36th Engineering - Platoon Battalion removed engineering equipment from the Kupa crossing , leaving behind only four to six boats . The command post of the 102nd Infantry Brigade remained in Farkašić , detached from the main offensive force in Stankovac . On 13 December , at approximately 07 : 00 , the independent HV armoured - mechanised unit advanced northwest along the Kupa , towards Gračanica . During the advance , one of the tanks was captured and its crew killed after the capture . Nearly simultaneously , the JNA commenced a tank and mortar attack against Stankovac and the river crossing at Šišinec . The HV armoured - mechanised unit and the 1st Battalion of the 102nd Infantry Brigade panicked , believing the crossing point was lost and start to fall back to Šišinec in disarray , sustaining considerable casualties . Since there was no way to transport the remaining HV armour across the Kupa River , the tanks were destroyed by one of the force ' s own tanks . The tank used to do that was blown up using explosives to prevent its capture . As there were too few boats at the river crossing to allow a quick retreat , some of the troops swam across the river , causing several to drown in very cold water . The command post of the brigade fell back to Galdovo , while the troops started to retreat to Zagreb . The entire brigade was back in Zagreb by 15 December . Aftermath . While the JNA ' s casualties are not known , the HV sustained a loss of 18 killed and 18 wounded , as well as a loss of eight tanks , two armoured personnel carriers and seven boats . The 2 , 011 - strong 102nd Infantry Brigade alone suffered 13 dead . Their names were later inscribed on a memorial plaque in Šišinec , at the Kupa River crossing point . In the aftermath of the offensive , there were speculations in Croatia that the casualties were much higher , possibly as many as 60 killed and 200 wounded . A Croatian Serb paramilitary unit " Šiltovi " , based in Glina , is suspected of killing of the HV troops taken as prisoners of war during the retreat . In addition , the Croatian Serb force killed 21 civilians in the Joševica massacre as a retribution for the HV offensive . The killing was investigated by SAO Krajina authorities , which concluded that the killings were in revenge for deaths of 21 Serb paramilitaries in the village of Gračenica in Operation Whirlwind . In 2010 , Croatian authorities charged six persons with war crimes committed in the village of Joševica . The failed offensive was investigated by the HV in 1991 and researched later by retired HV Brigadier Vlado Hodalj . He concluded that the offensive failed because of overall poor planning and preparation , specifically citing the lack of reconnaissance and reserves . Furthermore , Hodalj cited inadequate leadership by the Sisak OG as a cause of the failure , pointing to inaction in respect of the 10th Brigade ' s failure to advance and improper employment of the 2nd Guards Brigade in an auxiliary role , protecting the flank of an inexperienced brigade that was committed to the offensive with little , if any , training . Finally , the offensive itself had no clear goal . Croatian Admiral Davor Domazet - Lošo also criticised the offensive as an unnecessary , purely tactical and politically counterproductive move , likely unauthorised by applicable authorities . Hodalj praised the Sisak OG command for managing to keep the operation a secret until it was launched , making sure it would surprise the JNA . The secrecy was reflected in the apparent last - minute rerouting of the 102nd Infantry Brigade to the offensive , even though the Zagreb Operational Zone deployed it to Sunja , to the east of Sisak . Still , the Sisak OG failed to prepare detailed river crossing plans , or even issue maps and written brigade - level commands for the crossings — relying on oral commands instead . Likewise , the troops were not equipped to endure the cold weather in the open , limiting their effectiveness . Hodalj concluded that the offensive exceeded needs and capabilities of the Sisak OG . Even though the 1991 HV investigation concluded that the offensive was prepared for ten days and was approved by Zagreb Operational Zone command , there are no documents pertaining to the preparations other than those issued by the Sisak OG itself . Regardless of the poor preparation of the offensive , the 102nd Infantry Brigade was subject to public criticism in Croatia for fleeing the battlefield in the aftermath of Operation Whirlwind .