'Vollmond' was a German operation against the partisan forces of Marshal Josip Broz Tito in German-occupied Yugoslavia, and based on intelligence derived from decrypted partisan radio messages (8/11 June 1944).
'Vollmond' was planned and implemented by SS-Gruppenführer und Generalleutnant der Waffen-SS Karl-Gustav Sauberzweig’s 13th SS Gebirgsdivision 'Handschar' (kroatische Nr 1), with the goal of preventing partisan forces from advancing to the north toward Majevica, Posavina and Semberija. Launched at 03.45 on 8 June, the operation involved the 1 and 2/27th SS Gebirgsjägerregiment, supported by an artillery battery in Donja Trnova, attacking to the south in the direction of Visoka Glava and Jasenica, and the 1/28th SS Gebirgsjägerregiment, supported by two artillery batteries, holding the heights around Prboja before moving to link with the 4/28th SS Gebirgsjägerregiment in Lopare. The partisan forces involved were the 1st, 2nd and 4th Brigades of the 16th 'Vojvodina' Division, the 3rd and 5th Brigades of the 36th 'Vojvodina' Division, and the 17th 'Majevica' Brigade and the 'Posavina' Partisan Detachment of the 38th 'East Bosnia' Division.
The German plan was based on the expectation that the partisans would try to bypass Lopare and Priboj in their advance, but instead the partisans launched direct assault knowing that the 1/28th SS Gebirgsjägerregiment was manned largely by recruits forcibly drafted in Posavina and Majevica and lacking all but the most rudimentary training. The attack was launched by the 1st Brigade of the Yugoslav 16th Division at 18.00 on 8 June with its 4th and 5th Battalions attacking the 1/28th SS Gebirgsjägerregiment, and one hour later the 2nd Brigade of the same division joined in the attack.
After the operation Sauberzweig claimed that his forces had killed 3,000 partisans, while other German reports claimed 1,586 dead partisans in exchange for 205 Germans killed, 528 wounded and 89 missing from the 13th SS Gebirgsdivision. The 16th Division claimed to have inflicted 230 casualties (dead and wounded) and taken 30 prisoners in exchange for its 1st and 2nd Brigades' losses of 57 dead, 174 wounded and 26 missing.
A counterattack by the 2/28th SS Gebirgsjägerregiment prevented the 16th Division from exploiting its success.