Why did the United States and the Soviet Union divide Korea along the 38th parallel?

The division of Korea along the 38th parallel was established in August 1945 through General Order No. 1, which designated the line as the boundary for accepting the Japanese surrender: forces north of the line surrendered to the U.S.S.R., while those to the south surrendered to the United States.1

While some historians view this as a matter of military expediency, it is widely concluded that the primary motivation for the United States was to prevent the Soviet Union from occupying the entire Korean peninsula. U.S. policy during World War II sought to avoid the domination of Korea by any single power, and the establishment of the 38th parallel served as a strategic measure to halt the Soviet advance.1