inland as it moved through the mountainous eastern region of the country. The rugged terrain of the eastern regions of Korea, poor communication equipment, and unreliable resupply lines thwarted the South Korean resistance. The North Koreans used this to their advantage in advancing but they began to experience the same problems themselves. The 5th Division and the two other units began advancing south slowly and cautiously, sending strong reconnaissance parties into the mountains to ensure they would not be threatened from the rear. However, this more cautious advance began to give the South Koreans valuable time to build up further south. By June 28, the 766th had infiltrated into Taebaek-san from Uljin and was moving toward Ilwolsan, Yongyang and Cheongsong in order to block communications between Daegu and Busan, where United States Army forces were landing in an attempt to support the collapsing ROK Army. The ROK 23rd Regiment of the ROK 3rd Division was moved to block the advance of the three units at Uljin. The ROK forces mounted a series of delaying actions against the main North Korean force, which was significantly dispersed throughout the mountainous region and unable to muster its overwhelming strength. The ROK regiment was subsequently able to hold up the North Korean advance until July 5. On July 10, the 766th separated from the 5th Division and met an advance party of North Korean civilians in Uljin who had been sent to set up a government in the area. From here, the 766th dispersed in small groups into the mountains. On July 13 it reached Pyonghae-ri, north of Yongdok. Over the next week, the 766th Regiment and the KPA's 5th Division continued in slow advance south as it met increasing South Korean resistance. United Nations air support began to increase, slowing the advance further. The force continued to occupy the eastern flank, and by July 24 it was advancing from the Chongsong-Andong region and approaching Pohang. On its flank was the KPA's 12th Division. Progress halted as UN aerial and naval bombardment made movement more difficult. At the same time, the North Korean units' supply lines were stretched thin and began to break down, forcing them to conscript South Korean civilians to carry supplies. Resistance On July 17, the KPA's 5th Division entered Yongdok, taking the city without much resistance before fierce UN air attacks caused the division heavy losses. Still, it was able