Escalation of the Korean war

In the face of fierce North Korean attacks, the allied defense became a desperate battle called the Battle of Pusan Perimeter by Americans. However, the North Koreans failed to capture Pusan.

American air power arrived in force, flying 40 sorties per day in ground support actions[citation needed] Strategic bombers (mostly B-29s based in Japan) closed most rail and road traffic by day, and destroyed 32 critical bridges necessary for the conduct of warfare.[27]:47-48 Trains used by military and civilians alike waited out the daylight hours in tunnels.[27]:66

Throughout all parts of Korea, the American bombers knocked out the main supply dumps and eliminated oil refineries and seaports that handled imports. The bombing was designed to starve North Korean forces of ammunition and other martial supplies. Naval air power also attacked transportation choke points. The North Korean forces were already strung out over the peninsula, and the destruction caused by American bombers prevented needed supplies from reaching North Korean forces in the south.[27]:58

Meanwhile, supply bases in Japan were pouring weapons and soldiers into Pusan.[27]:59-60 American tank battalions were rushed in from San Francisco; by late August, America had over 500 medium tanks in the Pusan perimeter.[27]:61 By early September, UN-ROK forces were decidedly more powerful and outnumbered the North Koreans by 180,000 to 100,000. At that point, they began a counterattack.