South Korea maintains a political and security alliance with the United States since the Korean War and its major foreign policy issue remains North Korea. South Korea also has a complex relationship with Japan due to their shared history, including Japan's colonization of Korea from 1910 to 1945. While South Korea and Japan are important economic partners today, historical issues from World War II continue to strain their political ties. Both the U.S. and China play influential roles in the region as South Korea works to balance its relationships.