The terms Apostasia (, "Apostasy") or Iouliana (, "July events") or the Royal Coup ( To Vasiliko Praxikopima) are used to describe the political crisis in Greece centered on the resignation, on 15 July 1965, of Prime Minister Georgios Papandreou and subsequent appointment, by King Constantine II, of successive prime ministers from Papandreou's own party, the Centre Union, to replace him. Defectors from the Center Union were branded by Papandreou's sympathizers as Apostates ("renegades"). The Apostasia heralded a prolonged period of political instability, which weakened the fragile post-civil war order, and ultimately led to the establishment of the military regime in April 1967. Background Rise of Centre Union On September 19, 1961, Prime Minister Konstantinos Karamanlis called a general election (the elections were already expected to happen that autumn). The night of the same day, various factions of Greece's liberal centrist political forces, known as the "Center", joined together under the leadership of Georgios Papandreou into a new political party, the Centre Union (EK), whose aim was to provide a credible alternative to the National Radical Union (ERE). The elections of October 29th, led to a wide-margin victory for ERE. However, this was a result of election fraud and of a wide scale terrorism of left and center wing sympathizers by the police, military and paramilitary forces loyal to ERE. This terrorism included some assassinations of leftist EDA's supporters by the police and the military. Election fraud was widespread with votes by dead people being counted towards the election results and a case in which 218 police officers were registered in the same address, in a two-store detached house. As a result, Papandreou, other Centre Union politicians and the leftist EDA challenged the result and Papandreou, a gifted orator, launched a "Relentless Struggle" (Greek: Ανένδοτος Αγών) aimed at forcing the "illegal government" of Karamanlis from power. In May 1963, Karamanlis resigned officially over a dispute with King Paul on the latter's planned visit to the United Kingdom, but there has been speculation that the "Relentless Struggle" and other crises (most notably the assassination of the leftist independent MP Gregorios Lambrakis with the alleged involvement of the police and the secret service) had greatly weakened Karamanlis's position. A general election in late 1963 resulted in Centre Union coming first although without achieving an absolute majority. Papandreou was appointed prime minister and gained a vote of confidence in Parliament since the EDA