In early June the recently appointed UN commander, General Clark, made his first visit to the 1st Marine Division front. During his briefing, General Selden reviewed the unusual combat difficulties confronting his Marines. In addition to the unfavorable terrain, the division commander noted the special operational restrictions caused by proximity to the truce talk site. Presence of a large number of uncharted minefields created another obstacle. Herculean efforts were required of the Marines to simultaneously man and construct defenses over 35 miles of JAMESTOWN. Adding to Marine problems were the facts that ground units were not receiving sufficient close air support and the capabilities of the Chinese were constantly increasing. Chinese order of battle (OOB) information was fed into the division intelligence network by higher commands, I Corps and EUSAK, and adjacent units, but a large part of the data about Communist forces was produced by the division itself. Frontline units in contact with the enemy, by observation of his activities, supplied the bulk of intelligence about enemy defense tactics, employment of weapons, and combat characteristics. Supporting Marine division units, particularly artillery and armor, fed more facts into the system, mostly through identification of the caliber of enemy shells fired at the Marines. As a result of its missions forward of the line and actions in defense of it, the division reconnaissance company also contributed to the intelligence network. Individual Marines, performing as tactical air observers and artillery air observers, as well as the VMO and HMR pilots, were other important sources readily available to the 1st Marine Division. G-2 directed the division intelligence effort, including processing of raw material and supplying of updated reports to 1st Division units. The G-2 section also maintained OOB and target identification data on Chinese units and their commanders. Members of the G-2 staff also assisted in interrogation of prisoners of war (POWs), screened the civilians apprehended in unauthorized areas, debriefed Marines exposed to enemy intelligence, and conducted inspections of division internal security. In areas where the 1st Marine Division had only a limited intelligence capability it turned to EUSAK for assistance. Eighth Army teams augmented the division counterintelligence efforts and provided most of the translation service. In addition, three radio intercept units furnished information to the Marines. The critical importance of this service had been proven during several combat patrols in May when additional information was instantly radioed to a friendly unit under fire.