Case White, also known as the Fourth Enemy Offensive, was a combined Axis strategic offensive launched against the Yugoslav Partisans throughout occupied Yugoslavia during World War II. It was one of the most significant confrontations of World War II in Yugoslavia. The offensive took place in early 1943, between 20 January and mid-to-late March. The Axis operation prompted the Partisan Supreme Command to enact its plans to drive toward eastern Herzegovina, Sandžak and Montenegro.

World War II in the Kingdom of Yugoslavia began on 6 April 1941, when the country was invaded and swiftly conquered by Axis forces and partitioned among Germany, Italy, Hungary, Bulgaria and their client regimes. Shortly after Germany attacked the USSR on 22 June 1941, the communist-led republican Yugoslav Partisans, on orders from Moscow, launched a guerrilla liberation war fighting against the Axis forces and their locally established puppet regimes, including the Axis-allied Independent State of Croatia (NDH) and the Government of National Salvation in the German-occupied territory of Serbia. This was dubbed the National Liberation War and Socialist Revolution in post-war Yugoslav communist historiography. Simultaneously, a multi-side civil war was waged between the Yugoslav communist Partisans, the Serbian royalist Chetniks, the Axis-allied Croatian Ustaše and Home Guard, Serbian Volunteer Corps and State Guard, Slovene Home Guard, as well as Nazi-allied Russian Protective Corps troops.