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.