 On 9 August 1945, in the closing days of World War Two, the Soviet Union declared war on Japan and advanced into Korea.Though the Soviet declaration of war had been agreed by the Allies at the Yalta Conference, the US government became concerned at the prospect of all of Korea falling under Soviet control.The US government therefore requested Soviet forces halt their advance at the 38th parallel north, leaving the south of the peninsula, including the capital, Seoul, to be occupied by the US.