This was a German and Croat operation against the forces of Marshal Josip Broz Tito in the area to the west of Sesvete and Varaždin in the puppet state of Croatia in German-occupied Yugoslavia (15/18 May 1944).
The object of the undertaking was the destruction of the partisan forces (32nd and 33rd Divisions) in the area to the west of the road linking Sesvete and Varaždin between the Ivanščica and Zagrebačka mountain regions.
The Germans provided three battalions of ethnically German Croats of the Polizei-Freiwilligen-Regiment 'Kroatien', and the Croats the 1st Regiment of Ustaše Pukovnik Ante Moškov’s Poglavnik Bodyguard Division and the 2nd Ustaše Battalion of Ustaše Pukovnik Rafael Boban’s 5th Ustaše Brigade.
There was intense fighting during the operation, and by 17 May the Axis forces had driven the partisans back into the centre of the Kalnik mountain region around the town of Apatovac. General Dr Julius Ringel’s LXIX Corps claimed partisan losses of 552 counted dead, a further 700 to 800 estimated dead, and 61 captured. A brigade commander of the 32nd Division was killed and the deputy to the commander of the X Corps was severely wounded. The German and Croat losses amounted to four men killed and 15 wounded. The operation also freed 64 Croat and German military prisoners held by the partisans.