Korean War Begins - A poster with a picture of a world map

The Korean War began on June 25th, 1950 when the North Korean Communist army crossed the 38th Parallel and invaded non-Communist South Korea. As the North Korean army, armed with Soviet tanks, quickly overran South Korea, the United States came to South Korea’s aid. As the North Korean army, armed and trained by the USSR and supplemented by China, pushed into the South Korean capital of Seoul, the U.S. readied its troops and allies not just to fight on South Koreas behalf, but to fight a war against communism itself.
The Korean War was the first in which the United Nations played a role. Sixteen countries sent troops to aid South Korea, however 90% of the troops were from the United States. Officially, the Korean War has never technically ended since a formal peace treaty was never signed. Today, the two countries are separated by the Korean Demilitarized Zone (DMZ), a heavily patrolled border barrier that divides the Korean Peninsula roughly in half.