Peter II of Yugoslavia reigned as the last king of Yugoslavia from 9 October 1934 until his ousting from power on 29 November 1945. Considered the last reigning king of the Karađorđević dynasty, Peter II of Yugoslavia moved to the USA after his deposition where he suffered from alcoholism and depression.
Alexander I of Yugoslavia reigned as the king of Yugoslavia from 1921 until his death in 1934. During a state visit to France, Alexander was murdered by Bulgarian Vlado Chernozemski. The assassination inspired the opening of Christopher Hyde's book, The Second Assassin. Alexander's life and career inspired a TV series titled Alexander of Yugoslavia.
Quintillus was a Roman emperor for a brief period of time in 270 AD. He succeeded his brother Emperor Claudius Gothicus after the latter's death in 270. However, Quintillus' claim to the throne was challenged by Aurelian, who eventually succeeded him after a battle.
Stefan Dušan reigned as the King of all Serbian and Maritime Lands from 1331 to 1346. He then reigned as the Emperor of the Serbian Empire from 16 April 1346 until his death on 20 December 1355. Stefan Dušan was counted among the most powerful monarchs of his generation as he had conquered a major part of southeast Europe.
Milan I of Serbia reigned as the King of Serbia from 1882 until his sudden abdication in 1889. He abdicated in favor of Alexander I of Serbia, which was unexpected at that time. During his reign, Milan focused on developing natural resources and improving the means of communication. However, he was largely unpopular due to reckless extravagance and heavy taxation.
Hostilian reigned as the Roman emperor for a brief period from June to July 251. Prior to becoming the emperor, Hostilian had been elevated to caesar by his father and then-Roman Emperor Decius. When Decius and his older son Herennius Etruscus died at the Battle of Abritus, Trebonianus Gallus was proclaimed emperor and Hostilian was elevated to co-emperor.