Initially, after Mao and the People's Liberation Army (communists) overtook mainland China in 1949, the Nationalist government that had been in power (led by Chiang Kai-shek) fled to Taiwan. The PLA was a land army and not set up for an immediate attack by sea. Mao did intend to take Taiwan, though, but the US intervened in 1950 (under Truman) by sending a fleet to police the strait. There were various crises in the 50s, but the US always backed Taiwan, even threatening nuclear retaliation against the PRC. The US continued to supply defense and arms throughout the 60s as well. This was consistent with Cold War era attempts to stop the supposed spread of communism. In the 1970s, the policy shifted and the US (and UN) finally recognized PRC as a state, rather than Taiwan. Taiwan left the UN in protest and is considered part of the PRC by both China and the UN.