In June 1950, the Korean War began with a surprise attack by the North Korean people’s Army as North Korean soldiers crossed the 38th parallel, the boundary between the Soviet-backed Democratic People’s Republic of Korea to the north and the pro-Western Republic of Korea to the south. This invasion was the first military action of the Cold War. By July, American troops had entered the war as allies of South Korea. After an epic back-and-forth struggle across the 38th parallel, the fighting stalled and casualties mounted. In July 1953, the Korean War ended without either side achieving victory, and the Korean Peninsula remains divided today.