Park had come to power as the head of the Supreme Council for National Reconstruction after the May 16 coup of 1961, and in 1963 he won elections and assumed office as civilian president.
However, the National Assembly, dominated by Park's Democratic Republican Party, amended the Constitution in 1969 to allow a third term.
However, it did not reach the minimum condition to pass a constitutional amendment, which required the concurrence of two thirds or more of the total members of the National Assembly.
In December 1971, shortly after winning a third term, Park declared a state of emergency "based on the dangerous realities of the international situation".
In accordance with the Yusin Constitution, an electoral college called the National Council for Unification (통일주체국민회의, Tongil Juche Gungmin Hoeui) was set up.
In practice, the conference's power to appoint one-third of legislators was exercised by the president, guaranteeing him a parliamentary majority and control over parliament.
Park justified his creation of a legal dictatorship by arguing that South Korea's economy was too weak to allow Western-style liberal democracy.
The American Carter Administration warned that United States military forces might be withdrawn from South Korea unless Park eased off his dictatorship.