September 15
UN Forces Launch Inchon Landing in Korea
General Douglas MacArthur’s audacious amphibious assault at the port of Inchon outflanked North Korean forces and reversed the momentum of the Korean War.
Summary
The Korean War erupted in June 1950 when North Korean forces invaded South Korea, pushing UN-backed defenders back to the Pusan Perimeter in the southeast. General Douglas MacArthur, commanding UN forces, devised a bold amphibious counteroffensive to outflank the enemy near Seoul despite challenging tides and terrain at the port of Inchon. On September 15, after preparatory bombardments, U.S. Marines and South Korean troops of X Corps began landing in multiple waves under Operation Chromite, facing initial resistance at Wolmi-do Island before securing beachheads. The surprise assault rapidly overwhelmed North Korean defenses, allowing forces to recapture Seoul within days and cut supply lines. This operation reversed the war's momentum, forcing North Korean retreats northward. MacArthur's gamble succeeded due to meticulous planning and naval superiority.
Context
The Korean War began on June 25, 1950, when North Korean troops crossed the 38th parallel and rapidly overran much of South Korea. Republic of Korea forces, supported by the United States and other United Nations members, fell back under the pressure of superior North Korean numbers and equipment. By early August the defenders had been compressed into a defensive line known as the Pusan Perimeter in the southeastern corner of the peninsula.
What Happened
MacArthur, commanding United Nations forces from Tokyo, rejected a purely defensive strategy and instead ordered an amphibious counterstroke codenamed Operation Chromite. He selected the port of Inchon, west of Seoul, despite its extreme tidal range, narrow channels, and seawalls. Preparatory naval and air bombardments began on September 13, softening North Korean positions on Wolmi-do Island and the mainland.
Aftermath
On September 15, U.S. Marines of the 1st Marine Division, part of X Corps under Major General Edward M. Almond, first seized Wolmi-do in the morning. That evening the main landings occurred on Red and Green Beaches amid sporadic resistance. By September 19 Inchon was secure. UN forces then pushed inland, recapturing Seoul on September 28 and severing North Korean supply lines south of the capital.
Legacy
The operation relieved the Pusan Perimeter and enabled a rapid UN advance northward that nearly reached the Yalu River before Chinese intervention changed the war’s character. Inchon remains a textbook example of a successful large-scale amphibious flanking maneuver and reinforced the value of naval superiority and meticulous planning in modern warfare.
Why It Matters
The Inchon landing stands as one of history's most successful amphibious operations, altering the Korean War's course by relieving Pusan and enabling UN advances toward the Yalu River before Chinese intervention. It exemplified MacArthur's strategic boldness, influenced U.S. military doctrine on amphibious warfare, and highlighted the risks and rewards of flanking maneuvers in modern conflicts.
Related Questions
Why did MacArthur choose Inchon for the landing?
Inchon lay far behind North Korean lines near Seoul, allowing UN forces to cut supply routes and threaten the enemy rear while the Pusan Perimeter was still under siege.
What made the Inchon landing especially risky?
Extreme 30-foot tides limited landing windows, narrow approach channels were easily mined, and high seawalls surrounded the beaches, all of which North Korean defenders could exploit.
How large was the invasion force?
Approximately 75,000 troops supported by 261 naval vessels from the United States and allied nations participated in the operation.
What immediate effect did the landing have on the war?
North Korean units south of Seoul were isolated and forced into a disorganized retreat, relieving pressure on the Pusan Perimeter and enabling a UN counteroffensive.
Did the success at Inchon change U.S. military thinking?
The operation reinforced confidence in large-scale amphibious warfare and influenced postwar doctrine on the use of naval power to achieve strategic surprise.
Related Portfolio Site
US Military Atlas: Major U.S. military amphibious operation and turning point in the Korean War
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Sources
- Battle of Inchon, Wikipedia. Accessed 2026-07-04.