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 in the North African campaign. In operations Weiss I and Weiss II, the Wehrmacht did not achieve their desired goals of destroying the Yugoslav partisans and establishing control over the region, 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 the Eastern Front as reinforcements. Löhr entrusted the tactical command to the German troop commander in Croatia, Rudolf Lüters. The combat group for this operation was therefore called the Croatian Corps.
The German command adjusted the operational plan of action against Partisans to the characteristics of the terrain. They planned to concentrate main partisan divisions and their Supreme Headquarters on the naturally isolated and almost uninhabited area between the Tara and Piva canyons, and the Durmitor mountain, and to destroy it there with the mass use of aviation, artillery and mountain troops. The 1st Mountain Division with its northern wing, the Italian 19th Infantry (Mountain) Division Venezia, the battle group Ludwiger (724th German, 61st and 63rd Bulgarian Regiments), the 369th Infantry Division, the 118th Jäger Division with the 4th Home Guard Jäger Brigade of the Independent State of Croatia were deployed in a semicircle on the east and north sides. In the first phase, these forces were supposed to take control of Sandžak and push Partisan forces to the left side of River Tara. The southern wing of the 1st Alpine Division Taurinense, 23rd Infantry Division Ferrara and the 7th SS Mountain Division Prinz Eugen were supposed to push Partisans from the south and southeast. After that, the 118th Jäger Division had the task of occupying the left bank of the Piva and thus closing the environment, so that the breakthrough was hindered not only by strong forces but also by deep river gorges. This would bring Partisan forces to a dead end and destroy them.
In addition to these forces, there were additional 4 Italian divisions deployed in Adriatic hinterland, from the Albanian border to the lower course of the Neretva: were these Italian divisions: 155th Infantry Division Emilia in the Bay of Kotor, 151st Infantry Division Perugia in area of Vilusi, Bileća and Trebinje, 154th Infantry Division Murge around Dubrovnik and 32nd Infantry Division Marche in downstream of the Neretva, from Mostar to Metković.