On 9 August 1945 , in the closing days of World War II , the Soviet Union declared war on Japan and advanced into Korea , at the request of the United States . Though the Soviet declaration of war had been agreed by the Allies at the Yalta Conference , the US government had agreed with the Russian government earlier that the Soviet advance would stop at the 38th parallel , which it did . The US government forces arrived a few weeks later and occupied the area south of the 38th parallel , including the capital , Seoul . This was incorporated into General Order No. 1 to Japanese forces after the surrender of Japan on 15 August . On 24 August , the Red Army entered Pyongyang and established a military government over Korea north of the parallel . American forces landed in the south on 8 September and established the United States Army Military Government in Korea
Yalta Conference
Yalta Conference
Korean conflict