South Korea’s Key Strategic Military Advantage Over the North

South Korean marines participate in an amphibious landing operation with U.S. troops along Pohang seashore on April 2, 2017 in Pohang, South Korea. Chung Sung-Jun/Getty Images

On June 25, 1950, North Korea invaded the south, and its Soviet-supplied army smashed through South Korea’s defense.

Seoul fell within three days, and within five days South Korea’s army was shattered, losing nearly 80 percent of its 95,000 soldiers.