Royal Serbian Army in the context of "Chetniks in the Balkan Wars"

The May Coup (Serbian: Мајски преврат, romanized: Majski prevrat) was a coup d'état in the Kingdom of Serbia which resulted in the assassination of King Alexander I and his consort, Queen Draga, inside the Stari Dvor in Belgrade on the night of 10–11 June [O.S. 28–29 May] 1903. This act resulted in the extinction of the Obrenović dynasty that had ruled Serbia since the middle of the 19th century. A group of army officers led by Captain Dragutin Dimitrijević (Apis) organized the assassination. After the May Coup, the throne passed to King Peter I of the Karađorđević dynasty.

Along with the royal couple, the conspirators killed prime minister Dimitrije Cincar-Marković, minister of the army Milovan Pavlović [sr], and general-adjutant Lazar Petrović. The coup had a significant influence on Serbia's relations with other European powers; the Obrenović dynasty had mostly allied with Austria-Hungary, while the Karađorđević dynasty had close ties both with Russia and with France. Each dynasty received ongoing financial support from their powerful foreign sponsors.

Alexander I Karađorđević (Serbo-Croatian: Александар I Карађорђевић, romanized: Aleksandar I Karađorđević, pronounced [aleksǎːndar př̩viː karadʑǒːrdʑevitɕ]; 16 December 1888 [O.S. 4 December] – 9 October 1934), also known as Alexander the Unifier (Aleksandar Ujedinitelj / Александар Ујединитељ [aleksǎːndar ujedǐniteʎ]), was King of the Serbs, Croats and Slovenes from 16 August 1921 to 3 October 1929 and King of Yugoslavia from 3 October 1929 until his assassination in 1934. His reign of 13 years is the longest of the three monarchs of the Kingdom of Yugoslavia.

Born in Cetinje, Montenegro, Alexander was the second son of Peter and Zorka Karađorđević. The House of Karađorđević had been removed from power in Serbia 30 years prior, and Alexander spent his early life in exile with his father in Montenegro and then Switzerland. Afterwards he moved to Russia and enrolled in the imperial Page Corps. Following a coup d'état and the murder of King Alexander I Obrenović in 1903, his father became King of Serbia. In 1909, Alexander's elder brother, George, renounced his claim to the throne, making Alexander heir apparent. Alexander distinguished himself as a commander during the Balkan Wars, leading the Serbian army to victory over the Ottoman Turks and the Bulgarians. In 1914, he became prince regent of Serbia. During the First World War, he held nominal command of the Royal Serbian Army.

Alexander I (Serbian: Александар I Обреновић, romanized: Aleksandar I Obrenović; 14 August 1876 – 11 June 1903) was King of Serbia from 1889 until his death in 1903, when he and his wife, Draga Mašin, were assassinated by a group of army officers, led by Captain Dragutin Dimitrijević.

Dragutin Dimitrijević (Serbian Cyrillic: Драгутин Димитријевић; 17 August 1876 – 26 June 1917), better known by his nickname Apis (Апис), was a Serbian army officer and chief of the military intelligence section of the Royal Serbian Army general staff in 1913. He is best known as the main leader of the Black Hand, a paramilitary secret society devoted to South Slav irredentism that organised the 1903 overthrow of the Serbian government and assassination of King Alexander I of Serbia and Queen Draga. Many scholars believe that he also sanctioned and helped organize the conspiracy behind the assassination of Archduke Franz Ferdinand on 28 June 1914. This led directly to the July Crisis and the outbreak of World War I.

In 1916, the government in exile of Serbian Prime Minister Nikola Pašić, who considered Dimitrijević's refusal to compromise on South Slav irredentism to represent a serious threat to the secret peace negotiations taking place with Vienna during the Sixtus Affair, filed charges of high treason against the leadership of Unification or Death. Dimitrijević was tried in Thessaloniki before a Serbian Army court martial arraigned by his opponents within the Serbian government. He was found guilty of conspiring to assassinate both the Archduke and Prince Regent Alexander Karađorđević and executed by firing squad, along with two senior associates on 26 June 1917.

The Armed Forces of the Principality of Serbia (Serbian Cyrillic: Оружане снаге Кнежевине Србије, romanized: Oružane snage Kneževine Srbije) or Army of the Principality of Serbia (Serbian Cyrillic: Војска Кнежевине Србије, romanized: Vojska Kneževine Srbije), was the armed forces of the Principality of Serbia.

Founded in 1830, it became a standing army taking part in the Serbian–Ottoman Wars of 1876–1878, the first conflict in the nation modern history, after which the country gained its full independence. It was succeeded by the Royal Serbian Army.