badly defeated in the Battle of Osan on July 5, the first encounter between US and KPA forces. For the first month after the defeat at Osan, 24th Division was repeatedly defeated and forced south by superior KPA numbers and equipment. The regiments of the 24th Infantry were systematically pushed south in engagements around Chochiwon, Chonan, and Pyongtaek. The 24th made a final stand in the Battle of Taejon, where it was almost completely destroyed but delayed KPA forces from advancing until July 20. By that time, the Eighth Army's force of combat troops were roughly equal to KPA forces attacking the region, with new UN units arriving every day. North Korean advance With Taejon captured, KPA forces attempted to envelop the Pusan Perimeter. The KPA 4th and 6th Divisions advanced south in a wide flanking maneuver. The two divisions were forced to spread their units along a thin line, but managed to penetrate the UN's left flank with armor and superior numbers, repeatedly pushing back UN forces. UN forces were pushed back repeatedly before finally halting the KPA advance in a series of engagements in the southern section of the country. The 3rd Battalion, 29th Infantry Regiment, newly arrived in the country, sustained massive casualties at Hadong in a coordinated ambush on July 27 that opened a pass to the Pusan area. Soon after, KPA forces took Chinju to the west, pushing back the US 19th Infantry Regiment and leaving routes to the Pusan area open for more KPA attacks. US formations were subsequently able to defeat and push back the KPA on the flank in the Battle of the Notch on August 2. Suffering mounting losses, the KPA force in the west withdrew for several days to re-equip and receive reinforcements. This granted both sides a reprieve to prepare for the attack on the Pusan Perimeter. Emplacement of the 25th Infantry Division The Eighth Army commander, Lieutenant General Walton Walker, then ordered the US 25th Infantry Division, under Major General William B. Kean, to take up defensive positions on the Pusan Perimeter's southern flank west of Masan. By August 15, the 25th Infantry Division had moved into the line, but rough terrain west of Masan limited the choice of its positions. The mountain group west of Masan was the first readily defensible ground east of the Chinju pass. The mountain ridges of Sobuk-san dominated the area and protected