World War II: A group of Serbian-nationalist officers of the Royal Yugoslav Air Force carried out a coup d'état after Yugoslavia joined the Axis powers.

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.

Serbian nationalism asserts that Serbs are a nation and promotes the cultural and political unity of Serbs. It is an ethnic nationalism, originally arising in the context of the general rise of nationalism in the Balkans under Ottoman rule, under the influence of Serbian linguist Vuk Stefanović Karadžić and Serbian statesman Ilija Garašanin. Serbian nationalism was an important factor during the Balkan Wars which contributed to the decline of the Ottoman Empire, during and after World War I when it contributed to the dissolution of the Austro-Hungarian Empire, and again during the breakup of Yugoslavia and the Yugoslav Wars of the 1990s.

The Royal Yugoslav Air Force, was the aerial warfare service component of the Royal Yugoslav Army. It was formed in 1918 and existed until 1941 and the Invasion of Yugoslavia during World War II.

The Yugoslav coup d'état took place on 27 March 1941 in Belgrade, Kingdom of Yugoslavia, when the regency led by Prince Paul of Yugoslavia was overthrown and King Peter II fully assumed monarchical powers. The coup was planned and conducted by a group of pro-Western Serbian nationalist Royal Yugoslav Air Force officers formally led by the Air Force commander, General Dušan Simović, who had been associated with several putsch plots from 1938 onwards. Brigadier General of Military Aviation Borivoje Mirković, Major Živan Knežević of the Yugoslav Royal Guards, and his brother Radoje Knežević were the main organisers in the overthrow of the government. In addition to Radoje Knežević, some other civilian leaders were probably aware of the takeover before it was launched and moved to support it once it occurred, but they were not among the organisers. Peter II himself was surprised by the coup, and heard of the declaration of his coming-of-age for the first time on the radio.