The Korean War was fought in the context of the Cold War, a 44-year period of conflict which began in 1947...
The Cold War was a state of economic, political and military tension between the Unites States of America (USA) and its allies and the Union of Soviet Socialist Republics (USSR) and its allies. It ended in 1991 with the disintegration of the USSR.
The USA and the USSR were the two most powerful of the World War Two allies who defeated the Axis powers: Germany, Japan, Italy, Hungary, Romania and Bulgaria. After the war the two victors could not agree on the makeup of the post-war world. Tension first arose in Europe where their armies faced each other in 1945 after the defeat of Germany. The USSR organised its eastern European conquests into the Eastern Bloc, which by 1955 had a military alliance known as the Warsaw Pact. The USA and its allies formed the North Atlantic Treaty Organisation. Over time, the Cold War spread to Asia and Africa and most nations aligned either with the USA or the USSR. Sometimes each bloc was identified by its economic policy and was called either the 'capitalist western bloc' or the 'communist eastern bloc.' China, which participated in the Korean War, was a member of the eastern bloc. Those nations that did not wish to take sides formed the Non Aligned Movement.
Throughout the Cold War the USSR and the USA were wary of directly confronting one another militarily as both had a well-founded fear that this would escalate into a nuclear war. Instead, wars by proxy occurred. The first one was the Korean War. Proxy wars were characterised by the overlay of domestic friction, such as that between North and South Korea, with the worldwide contest between the USA and the USSR.
At the end of WWII an agreement was made to temporarily split Korea into two administrations along the 38th parallel, dividing the country into north and south. The two superpowers supported their allies and client states with financial aid, military technology and training. Joseph Stalin, the leader of the USSR, backed Kim Il-Sung, a North Korean communist, while President Truman of the USA backed Syngman Rhee, the anti-communist first president of South Korea.
The USSR provided support to North Korea when it invaded the south. Within days of the 25 June 1950 invasion the USA declared its intent to stand by South Korea. The USA won the support of the United Nations Security Council which condemned the invasion, and endorsed the USA plan to send troops to defend South Korea. Australia was one of the 16 United Nations members who responded by sending land, sea and air forces.