The Korean War commenced when North Korean forces initiated a full-scale invasion of South Korea on June 25, 1950. The invasion was marked by a rapid advance of troops crossing the 38th parallel, the boundary established at the end of World War II that divided the Korean Peninsula into two separate states: communist North Korea and capitalist South Korea. North Korean leader Kim Il-sung planned the attack with the intention of unifying Korea under his regime, capitalizing on perceived weaknesses in the South's military preparedness. The invasion included a combination of infantry and armored divisions, employing tanks and artillery to significant effect, which led to swift territorial gains.In the early hours of the attack, cities like Seoul were targeted, creating panic and chaos. The South Korean military, unprepared for the assault, initially struggled to counter the invasion. As the situation escalated, the United Nations, led by the United States, quickly condemned the North's aggression, calling for international intervention. The U.S. President Harry S. Truman decided to send military assistance to South Korea and urged other nations to do the same. By the end of June 1950, U.S. forces were landing in South Korea to assist in the defense against the invasion.The onset of the Korean War was pivotal, as it marked the first significant armed conflict of the Cold War, demonstrating the stark ideological divisions between communism and democracy. The conflict not only involved Korean forces but also drew in international powers, leading to a bloody standoff and prolonged engagement between North and South Korea, supported by their respective allies. The war culminated in a military stalemate, with a ceasefire agreement signed in 1953, but no formal peace treaty was ever established.