It was Sunday. All the soldiers and citizens of South Korea were ready to enjoy their day off, when the North Korean military crossed the 38th parallel (the boarder-line between the two Koreas) at the break of dawn on June 25, 1950. A war broke out that lasted for three years and ten months, ruining the entire country. The war is known as the Korean War and is often called as "6.25" by Koreans.
Although the war is primarily remembered for the incident itself, a long story and a deeper meaning lies behind the Korean War. After the liberation of Korea from the occupation of Japan, Korea was divided into the North and the South. As the two separated, the North became occupied by the Soviet Union and the South, occupied by the United States, in accordance with an agreement put forth by the United States Government. As a result, the northern part of the country became a communist country whereas the south became a democratic country. With the help of the Soviet Union, Kim Il-sung, the ruler and general of the North, invaded the South to make the entire country a communist country and this is how the three-year long war began. In time, the army of the United Nations also came to help the South.
Within three days, Seoul was conquered by the Northern soldiers and people in the South began an exodus toward the southern end of the peninsula. Lee Syng-man, then president of South Korea, panicked by the sudden attack, immediately asked the U.S. for help. Three days after the war broke out, U.S. troops joined the Southern soldiers.
However, on July 20, the North continued their attacks and conquered Daejon. Then in August, the situation worsened for South Korea to a point where the last two free regions, Daegu and Busan, were in danger of being defeated. While the Northern soldiers were concentrating on fighting the forces at the bottom tip of the country, General McArthur, an American general, landed in Incheon with naval and close air support, outflanking the North Koreans and forcing them to retreat northward in disarray.
By September 28, 1950, the South Korean and allied forces finally won back Seoul and continued to head north at which almost a million Chinese soldiers unexpectedly joined the North Korean forces. However, the North Korean and Chinese militaries suffered a significant loss in manpower and national strength, and there was an increasing concern of the possible expansion of the war to a world war. Thus, on July 10, 1951, the first ceasefire negotiation was held in Gaesung.
Finally, on July 27, 1953, a ceasefire was finalized with the signing of the Armistice Agreement between the North and South, which resulted in a state of stalemate with no guarantee of the peninsula's peace and stability. As such, the two Koreas still remain separated to this day.