World War II: Thousands of civilians in German-occupied Serbia are murdered in the Kragujevac massacre.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The Territory of the Military Commander in Serbia was the area of the Kingdom of Yugoslavia that was placed under a military government of occupation by the Wehrmacht following the invasion, occupation and dismantling of Yugoslavia in April 1941. The territory included only most of modern central Serbia, with the addition of the northern part of Kosovo, and the Banat. This territory was the only area of partitioned Yugoslavia in which the German occupants established a military government. This was due to the key rail and the Danube transport routes that passed through it, and its valuable resources, particularly non-ferrous metals. On 22 April 1941, the territory was placed under the supreme authority of the German military commander in Serbia, with the day-to-day administration of the territory under the control of the chief of the military administration staff. The lines of command and control in the occupied territory were never unified, and were made more complex by the appointment of direct representatives of senior Nazi figures such as Reichsführer-SS Heinrich Himmler, Reichsmarschall Hermann Göring, and Reichsminister Joachim von Ribbentrop. The Germans used Bulgarian troops to assist in the occupation, but they were at all times under German control. Sources variously describe the territory as a puppet state, a protectorate, a "special administrative province", or describe it as having a puppet government. The military commander in Serbia had very limited German garrison troops and police detachments to maintain order, but could request assistance from a corps of three divisions of poorly-equipped occupation troops.