colonial rule and the separation of Rwanda and Burundi. The first and largest of these political parties was the Union for National Progress (UPRONA). Burundi's push for independence was influenced by the Rwandan Revolution and the accompanying instability and ethnic conflict that occurred there. As a result of the Rwandan Revolution, many Rwandan Tutsi refugees arrived in Burundi during the period from 1959 to 1961. Burundi's first elections took place on 8 September 1961 and UPRONA, a multi-ethnic unity party led by Prince Louis Rwagasore won just over 80% of the electorate's votes. In the wake of the elections, on 13 October, the 29-year-old Prince Rwagasore was assassinated, robbing Burundi of its most popular and well-known nationalists. The country claimed independence on 1 July 1962, and legally changed its name from Ruanda-Urundi to Burundi. Burundi became a constitutional monarchy with Mwami Mwambutsa IV, Prince Rwagasore's father, serving as the country's king. On 18 September 1962 Burundi joined the United Nations. In 1963, King Mwambutsa appointed a Hutu prime minister, Pierre Ngendandumwe, but he was assassinated on 15 January 1965 by a Rwandan Tutsi employed by the US Embassy. The assassination occurred in the broader context of the Congo Crisis during which Western anti-communist countries were confronting the communist People's Republic of China as it attempted to make Burundi a logistics base for communist insurgents battling in Congo. Parliamentary elections in May 1965 brought a majority of Hutu into the parliament, but when King Mwambutsa appointed a Tutsi prime minister, some Hutu felt this was unjust and ethnic tensions were further increased. In October 1965, an attempted coup d'état led by the Hutu-dominated police was carried out but failed. The Tutsi dominated army, then led by Tutsi officer Captain Michel Micombero purged Hutu from their ranks and carried out reprisal attacks which ultimately claimed the lives of up to 5,000 people in a precursor to the 1972 Burundian Genocide. King Mwambutsa, who had fled the country during the October coup of 1965, was deposed by a coup in July 1966 and his teenage son, Prince Ntare V, claimed the throne. In November that same year, the Tutsi Prime Minister, then-Captain Michel Micombero, carried out another coup, this time deposing Ntare, abolishing the monarchy and declaring the nation a republic, though his one-party government was effectively a military dictatorship. As president, Micombero became an advocate of African socialism and received support from