The Soviet Union backed North Korean troops wage war on the US-backed South Korean troops.
War began when the North Korean Communist army crossed the 38th Parallel and invaded non-Communist South Korea. As Kim Il-sung's North Korean army, armed with Soviet tanks, quickly overran South Korea.
The US tried using strategic bombing to intimidate the Communists into negotiating a peace treaty, but they wouldn't budge.
North Korea attacks and takes control of south Korea's capital eoul
Having made this landing, MacArthur crushed the North Korean army in a pincer movement and recaptured Seoul, the capital of South Korea.
After weeks of figuring out a treaty the war ends. They call a cease-fire that is still going on today. The border didn't move an inch.