The Pusan Perimeter Battles
Before the Marines could launch their counteroffensive, they first had to help hold the line. By early August 1950, UN forces had been pushed into a 140-mile defensive pocket in southeastern Korea known as the Pusan Perimeter. The situation was dire: North Korean forces had advanced rapidly, threatening to overrun the last stronghold of the Republic of Korea and its allies.
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To reinforce the crumbling front, the 1st Provisional Marine Brigade, built around the 5th Marine Regiment, landed at Pusan on August 3, 1950. Their mission was clear—stop the North Korean advance and stabilize the perimeter. Marines were thrown into fierce battles along the Naktong River, particularly at Obong-Ni Ridge, where they executed flanking maneuvers under intense fire to repel enemy forces.
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Despite being outnumbered and operating in rugged terrain, the Marines’ aggressive tactics and discipline helped blunt repeated North Korean offensives. Their actions bought precious time for UN forces to regroup and prepare for the Inchon landing. The defense of Pusan was a testament to the Marines’ ability to fight under pressure and adapt to rapidly changing battlefield conditions.