June 25, 1950 - 1953
The underlying reason that the Korean War broke out was because it was just another episode in the ongoing Cold War between the USA and the USSR.To the World, the Korean War looked like a war between South Korea and North Korea, but really the superpowers were just using it as an excuse to combat each other without really going into a war.
3 Reasons The U.S. Entered The Korean war
1st - The Domino theory. In the Far East, they were becoming powerful. Truman believed that, if one country fell to Communism, the others would follow, like a line of dominoes. He was worried if Korea fell, next would be Japan, which at the time was important to American trade. This was probably the biggest reason for America’s involvement.
2nd - President Truman believed that capitalism and the american way of life were in danger of being overrun by Communism. The Truman Doctrine was one of ‘containment’ stopping the communists gaining any more territory. This led Trumans consideration in driving the communists out of North Korea.
3rd - and finally, by supporting South Korea, America was able to fight communism without attacking Russia directly.