Case Black (), also known as the Fifth Enemy Offensive () in Yugoslav historiography and often identified with its final phase, the Battle of the Sutjeska ( ) was a joint attack by the Axis taking place from 15 May to 16 June 1943, which aimed to destroy the main Yugoslav Partisan force, near the Sutjeska river in south-eastern Bosnia. The failure of the offensive marked a turning point for Yugoslavia during World War II. It was also the last major German-Italian joint operation against the partisans. The operation immediately followed Case White which had failed in accomplishing the same objectives: to eliminate the central Partisan formations and capture their commander, Josip Broz Tito. Background During the previous operation Weiss, Chetniks fought against Partisans under Italian command. However, even during the operation, negotiations were held between the German and Italian leaders on the disarmament of the Chetniks. German Wehrmacht deeply believed that the Allies would invade the Balkans after victory at North African campaign. In operations Weiss I and Weiss II, the Wehrmacht did not achieve desired goals and did not destroy partisans, so preparations began for a new venture. With operation Schwarz, the Wehrmacht intended to clear the background of the Adriatic coast by destroying both the Chetnik and Partisan movements, which were still firmly established in Herzegovina and Montenegro. Hitler calculated that, in the event of a British invasion of the Balkans, Chetniks under Italian care would switch sides and join the Allies. However, in the first phase, there were tensions and misunderstandings between the German and Italian armies on that issue. Since the Italian commanders in Yugoslavia were very reluctant to disarm the Chetniks, Hitler won the consent through Mussolini's government and the General Staff. General Mario Robotti was fiercely against the disarmament of the Chetniks, at least until the partisans were destroyed. This attitude was shared by Chief of the Italian General Staff of the Land Army, general Vittorio Ambrosio, but he had to obey the promise that Mussolini gave to Hitler. At the beginning of March 1943, general Ambrosio, summoned Robotti and Alessandro Pirzio Biroli to Rome for talks on the disarmament of Chetniks and operations against partisans. Axis plans The Axis rallied 127,000 land troops for the offensive, including German, Italian, Croatian, Bulgarian, and over 300 airplanes. For this operation, the Commander of the Southeast, colonel-general Alexander Löhr, received elite 1st Mountain Division from