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Few major victories have generated as much controversy as the Sept. 15, 1950, invasion of Inchon, South Korea; but then, few American military leaders have sparked such debate as General Douglas A. MacArthur. At Inchon he gambled on an amphibious landing to change the course of the Korean War. That gamble paid off but may have led to a strategic miscalculation of even greater proportions.

On June 25, 1950, North Korean leader Kim Il-sung launched a full-scale invasion across the 38th parallel into South Korea. Seoul fell quickly, and weak U.S. forces intervened under the United Nations flag. By late July the North Korean People’s Army (NKPA) had pushed U.N. and Republic of Korea (ROK) forces into a pocket on the southeast corner of the peninsula that became known as the Pusan Perimeter, after the port city at its heart.

U.S. Commander in Chief, Far East, MacArthur was tapped to head United Nations Command and arrived in Korea in late June. He had few available ground forces but concluded that command of the sea gave him the advantage of strategic mobility. Exploiting this advantage would be the key to victory. He decided on an amphibious assault behind NKPA lines to liberate Seoul and cut North Korean supply lines. After studying several alternatives, he settled on the port of Inchon.

Critics found numerous flaws in MacArthur’s plan, pointing out that Inchon would be easy to defend. The approaches to the port were narrow and easily mined, and troops would have to debark at port facilities, along seawalls or in mudflats. The landing could only occur on a rising tide—limiting possible dates to three or four days per month. Finally, defenses built by the Japanese during World War II overlooked the harbor. A strong and determined North Korean defense could doom the landing.

MacArthur ignored his critics and the potential for strong enemy opposition, and set the invasion for September 15. He then turned over operational planning to the U.S. Navy. Seeking to divert enemy attention from Inchon, naval and air forces conducted raids on Kunsan, 100 miles farther south. These operations had mixed results, and intelligence leaks led cynics to dub the venture “Operation Common Knowledge.” There is some evidence the North Koreans learned the landing would be at Inchon, but they were slow to react.

Navy planners had their hands full even without worrying about the enemy response. Task Force 90 (TF 90), the amphibious fleet carrying the invasion force, had to transport 53,000 men in two divisions (1st Marine and the Army’s 7th Infantry) and associated forces, plus thousands of tracked and wheeled vehicles and some 25,000 tons of food, fuel and ammunition. Weather was the greatest danger. Typhoons raged through the region in early September, and it was only by sailing from Japan a day early that the ships avoided being engulfed by Typhoon Kezia. TF 90 narrowly escaped disaster but still suffered badly from the storm. MacArthur, who accompanied the invasion force, became desperately seasick. He returned to deck just in time to observe the main naval bombardment on September 14.

The landing was well executed. Naval guns devastated enemy shore batteries and harbor defenses, and aircraft supported the landing. Marines occupied the port and beaches, making use of lessons learned in World War II’s Pacific Theater. The landing force, X Corps, overwhelmed the NKPA defenders and drove inland over the following days as U.N. and ROK troops broke out of the Pusan Perimeter. Seoul fell on September 29, and MacArthur’s forces pursued the North Koreans toward the Yalu River.

Inchon was a decisive military victory in the short term and a fitting cap to MacArthur’s career. The entire campaign up to the fall of Seoul cost just over 3,000 U.N. casualties, against more than 20,000 North Koreans. Although the NKPA remained intact, with significant reserves, the campaign led directly to the liberation of South Korea.

Unfortunately, Inchon engendered overconfidence, leading MacArthur and the Truman administration to endorse a bold drive north to the Yalu in hopes of uniting the peninsula under a Western-oriented regime. Just as he had discounted NKPA opposition at Inchon, MacArthur dismissed the possibility of Chinese military intervention in the conflict. In October, however, Chinese forces surged across the Yalu, nearly overwhelming the Marines at Chosin and forcing a retreat back to the 38th parallel. This strategic defeat outweighed the victory at Inchon, in part leading to MacArthur’s dismissal. Years of stalemate would follow.


Originally published in the November 2012 issue of Military History. To subscribe, click here.