The Soviet Union and the United States left the Korean Peninsula at the end of 1948 and June 1949, respectively, leaving behind military advisors. However, in April 1950, Kim Il-sung won Stalin’s approval to invade the South on the condition that China agrees.

The sudden attack began on June 25, 1950 all along the 38^th parallel from the Ongjin Peninsula on the west coast to the east coast. South Korea lost its capital Seoul to the North’s far superior forces in just three days. In a month’s time, the North’s forces reached the Nakdong River.