766th Regiment was detached and sent on a mission to infiltrate Pusan. Paired with additional support, it formed the 600-man 588th Unit. 588th Unit was tasked with raiding Pusan harbor, destroying vital facilities to make it impossible for UN forces to land troops there. However, the troop transport carrying the 588th Unit was discovered and sunk by United Nations ships outside Pusan harbor the morning of June 25, destroying the 3rd Battalion. Outbreak Around 04:00 on June 25, the KPA's 5th Division began its first attacks on the ROK 10th Regiment's forward positions. Three hours later, the 766th Regiment's two battalions landed at the village of Imwonjin, using motor and sail boats to land troops and mustering South Korean villagers to assist in setting up supplies. The two battalions separated; one headed into the T'aebaek Mountains and the second advanced north toward Samcheok. At this point, the ROK 8th Division, under heavy attack from the front and aware of attacks in the rear, urgently requested reinforcements. It was denied these reinforcements, as ROK higher commanders informed the division commander that the ROK Army was under heavy attack across the entirety of the 38th parallel and had no reinforcements to spare. The ROK 21st Regiment, 8th Division's southernmost unit, moved to counter the amphibious attack. The regiment's 1st Battalion moved from Bukp'yong into the Okgye area and ambushed forward elements of the 766th in conjunction with local police and militia forces. They were able to drive back the 766th Regiment's northern advance. However, at least one of the 766th Regiment's battalions massed at Bamjae, blocking one of the 8th Division's main supply routes. ROK troops mustered a civilian militia to help fight the North Koreans, which was only moderately effective. The embattled ROK 8th Division was forced to withdraw under overwhelming attacks and breakdowns in communication on July 27. With the retreat of the ROK 6th Division, the entire ROK eastern flank was forced back. The 766th Regiment had been successful in establishing a bridgehead and disrupting communications in the initial attack. Advance With the ROK army in retreat, the 766th Regiment, 549th Unit, and KPA's 5th Divisions all advanced steadily south along the eastern roads without encountering much resistance. Across the entire front the North Korean Army had successfully routed the South Koreans and was pushing them south. The 766th Regiment acted as an advance force, attempting to infiltrate further