Other intelligence activities were less beneficial to the Marines. These operations were conducted by Tactical Liaison Officers (TLOs, friendly Koreans trained by U.S. intelligence teams), and members of a Higher Intelligence Detachment (HID), a Korean unit assigned from EUSAK. Both the TLO and HID proved of limited value to the division, due to the generally poor educational background of the agents, their inadequate training, and frequent failure to return from assignments behind enemy lines. Some Marines believed the basic fault in these operatives lay in “an exaggerated opinion of their importance.”[134] [134] _PacFlt EvalRpt_ No. 4, p. 9-33. Several division intelligence Marines, in conjunction with training and shore party personnel, took part in an informational activity of a different type. These Marines reconnoitered several friendly islands off western Korea to determine their suitability for division landing exercises. The second one inspected, Tokchok-to, 30 miles southwest of Inchon, was selected. By early June planning had progressed to the point where a program had been developed for bimonthly battalion landing team exercises. The KPR maneuver force, appropriately reinforced, was designated as a participating unit. Landings were to employ boat teams, amphibian tractors, and helicopters. The entire program was designed to provide refresher training for Marines in carrying out their primary mission of amphibious assault. By the end of June, 3/5 and 3/1, in turn, had captured Tokchok-to. Other training concentrated more on the task at hand. Division units in reserve rehearsed tactics for offensive and defensive warfare. Most ground units conducted extensive schooling in both mine and booby trap detection and clearance. Recognizing that patrolling was an important part of a Marine’s life on the MLR, the division included in its Noncommissioned Officers’ (NCO) Leadership School a thorough indoctrination in patrolling tactics.[135] More than 50 percent of the training at all levels was at night. In addition, an extensive orientation was conducted for newly arrived combat replacements, who could not be committed to action for 72 hours after joining the division. [135] BGen Austin R. Brunelli ltr to Hd, HistBr, G-3 Div, HQMC, dtd 13 Sep 66, hereafter _Brunelli ltr_. The division chief of staff during more than half of 1952, Colonel Brunelli later observed that the “school produced more effective patrolling and ... contributed to reducing our casualties.”