On the night 13/14th October 1950 soldiers of the Chinese People's Liberation Army (PLA) crossed the Yalu river from north-east China into Korea. In the 10 weeks of operations that followed, these men, with others crowding in behind them, threw back the powerful divisions of the United Nations Command, ejecting them from the territory of North Korea and, further, seemed capable of driving them from the whole Korean peninsular. No doubt the government in Beijing believed for a time that its soldiers were once more about to deliver an immense political prize to Party and state. They were wrong. If the intervention of the PLA changed the course of the Korean war initially much as Mao Zedong intended, it changed also the outlook of the PLA, led to factionalism among the military leadership, which persists and, arguably, accelerated the subsequent rift between China and the Soviet Union.