Although Belgian rule did little to defuse the tension between the two rival dynasties--the Bezi and the Batare--the legislative elections of 1961 resulted in a landslide victory for the representatives of the ruling Bezi dynasty, identified with the UPRONA, whose leader at the time was Prince Rwagasore, the eldest son of Mwami (King) Mwambutsa. Rwagasore was the embodiment of populist aspirations and the strongest supporter of the monarchy. His assassination on October 13, 1961, ushered in a crisis of legitimacy from which the country has yet to recover.
The turning point came on October 18, 1965, when a group of Hutu officers unsuccessfully tried to overthrow the monarchy, yet came close enough to realizing their objective to cause the panic-stricken Mwambutsa to flee the country. By then the inability of the crown to handle the competing claims of the Hutu and Tutsi had become palpably clear. The assassination by a Tutsi gunman of Pierre Ngendandumwe, the Hutu prime minister, on January 15, 1965, provided dramatic evidence of the spillover of ethnic hostilities from the UPRONA into the government. The critical factor behind the abortive coup, however, was Mwambutsa's decision to ignore the results of the May 1965 elections, which had given the Hutu 23 seats in the National Assembly out of a total of 33. By appointing his private secretary, Léopold Biha, as prime minister, Mwambutsa had made it unequivocally clear that power would continue to rest with the crown.
In the complicated sequence of events that followed the abortive coup, some 34 Hutu officers were executed in the first of a series of steps intended to give Tutsi elements unfettered control of the government. The second came in July 1966, when Michel Micombero was appointed prime minister. A Tutsi-Hima from Bururi province, Micombero had played a key role in thwarting the 1965 coup and in organizing anti-Hutu pogroms in the countryside. Finally, with the formal overthrow of the monarchy in November 1966--less than three months after the official transfer of the crown from Mwambutsa to his younger son, Prince Charles Ndizeye--and the formal proclamation of the First Republic, the last obstacle in the path of Tutsi hegemony was removed.