This was a German four-phase operation against the partisan forces of Marshal Josip Broz Tito in the Fruška mountain region of Syrmia in German-occupied Yugoslavia (14 June/6 August 1944).
The operation was designed to comb the Fruška mountain region and most of the rest of Syrmia in an attempt to pin and destroy mobile partisan forces operating in that area as these were making constant attacks on communications and traffic on the vital route linking Belgrade and Vinkovci; the operation’s secondary objective was to secure and collect the local harvest.
The undertaking involved between 10,000 an 15,000 German and Croat troops, most notably elements of SS-Brigadeführer und Generalmajor der Waffen-SS Desiderius Hampel’s 13th SS Gebirgsdivision ‘Handschar’ (kroatisch Nr 1), 606th Sicherungsregiment, and 1st, 2nd and 3rd Polizei-Freiwilligeregimenter ‘Kroatien’ supported by Croat forces including Pukovnik Gjurgjević's 7th Garrison Brigade, the Air Force School Regiment and the 6th Ustaše Battalion.
The operation was not successful, for its target, the 6th ‘Vojvodina’ Brigade, retreated into south-western Syrmia, on its way attacking the German garrison at Calma, and one battalion of the 1st ‘Syrmia’ Partisan Detachment retreated into south-eastern Syrmia. On 2 July the 7th ‘Vojvodina’ Brigade was formed with one Russian battalion manned by Soviet troops who had been captured by the Germans and used as slave labour but then escaped to or been captured by the partisans.
As a first step in the Axis effort, blocking lines were established round the main partisan area of the Fruška mountain area, the Bosut forest and south-eastern Syrmia. The partisan staff for Vojvodina learned of the imminent offensive through a captured Axis agent, and therefore ordered the 6th ‘Vojvodina’ Brigade and the 1st ‘Syrmia’ Partisan Detachment to retreat to the south-west to the Bosut forest and join the 2nd ‘Syrmia’ Partisan Detachment in order to carry out sabotage efforts, while single battalions of these units were reserved at Fruška to provide security the general staff infrastructure.
Starting on 14 June, the first phase of the Axis operation, an eastern group of some 5,000 men advanced toward the Fruška mountain region along the axis from Irig to Sremska Kamenica, and reached the line between Vrdnik and Rakovac on the same day. During the next day the eastern group reached the line between Beočin and Jazak, and dug in to serve as blocking force. At much the same time a western group of some 4,000 men started from line linking Šid and Ilok and moved forward with great care to search the area for partisans in the time up to 22 June, when it linked with the eastern group. However, the slow pace of the Axis advance made it possible for most of the partisans to escape and also establish ambushes. The partisans lost only six men. Despite the care of the partisans preparations, the Germans nonetheless managed to find several bases and capture around 80,000 rounds of small arms ammunition, two mortars, some shells, several tents and archives. Prisoners included 62 and 30 recently mobilised men from Sremska Mitrovica and Irig respectively, as well as another seven from a medical training camp, which also lost two persons killed. The 2nd Battalion of the 6th ‘Vojvodina’ Brigade lost several soldiers in an ambush.
The Axis operation’s second phase lasted from 1 to 12 July in north-eastern Syrmia and Podunavlje (Danube river basin), where no partisan units were located, so it was limited to looting anything of utility from a population suspected of supporting the partisans. The partisans made use of this period to carry out raids from the Bosut forest. On 2 July the 7th ‘Vojvodina’ Brigade was formed with Soviet prisoners, as noted above. The 2nd Battalion of the 6th ‘Vojvodina’ Brigade was ordered to return to its designated operational area in the Fruška mountain region by breaking through the Axis lines between Gibaraca and Bačinici. As the partisans did this, the Axis forces lost three men wounded and one captured, while the partisans lost one person killed and one captured. The Germans came to believe that some 2,000 to 3,000 partisans had sought to reach the Fruška mountain region but been repulsed.
The third phase of the Axis operation started on 6 July in south-eastern Syrmia. The partisans made attacks from the Fruška mountain region, and on the night of 10/11 July the 6th ‘Vojvodina’ Brigade attacked the German garrison of Čalma, comprising one company of the 606th Sicherungsregiment and about 100 collaborators. The partisan attack was repulsed, but nonetheless cost the Axis forces 19 men killed, eight wounded and nine captured, while the partisans lost suffered only three persons wounded. These attacks forced the Germans to organise a new effort to clear the Fruška mountain region as it had become clear that the first phase of ‘Kornblume’ had failed. Two groups, comprising 4,000 and 2,000 men, started a fresh attack on 17 July, but were driven back in several ambushes with the partisans claiming 250 killed and 270 wounded Axis troops for the loss of only 24 of their own killed and 36 wounded: the Croats claimed to have killed 398 partisan known dead, 600 estimated dead and 22 captured. Even as these overt military actions were prosecuted, both sides struggled to secure as much of the grain harvest as possible, and to destroy whatever these could not seize.
The fourth phase of the Axis operation began on 26 July as German forces moved from the Fruška mountain region toward south-western Syrmia. The 7th ‘Vojvodina’ Brigade, together with the 2nd ‘Syrmia’ Partisan Detachment and ‘Majevica’ Partisan Detachment, the latter newly arrived from eastern Bosnia, retreated into Slavonia and until 9 September fought as part of the VI Corps. Thus the Axis forces had managed to seize part of the harvest, but signally failed to remove the partisan threat to the communications between Belgrade and Vinkovci and between Belgrade and Novi Sad, and also to suppress the Yugoslav resistance in this region.