A second type of Marine close air support aided the mission of Marine infantrymen in western Korea during the summer of 1952. This was controlled radar bombing, which permitted delivery of aviation ordnance at night or under other conditions of limited or poor visibility. The Air Force had introduced the concept into Korea in January 1951, had tested and evaluated it in combat, and shortly thereafter had put it to good use against the Communist spring offensives that year. Based on a concept oriented towards deep support of troops in extended land campaigns, the Air Force system made use of 20-ton vans to house its ground components.[87] [87] As an Air Force spokesman noted, “... the AN/MPQ-2 radars introduced into Korea in January 1951 were Strategic Air Command bomb scoring radars and not tactical equipment. This would explain the large vans.” Robert C. Futrell, Historian, Hist Studies Br USAF Hist Div, comments on draft MS, dtd 12 Oct 66. Dr. Futrell authored the definitive unclassified history of Air Force operations in Korea, previously cited as _USAF, Korea_. The Marine equipment, on the other hand, was more mobile since it was to be employed close to friendly lines. Referred to as the MPQ-14,[88] the Marine radar bombing system was designed so that the largest piece could be put into a one-ton trailer. Major ground items were a generator power supply, a tracking radar, and a computer; the last essential component, an automatic bombing control, was mounted in the aircraft. [88] These letters indicate first, the type of installation; next, the kind of electronic equipment; and finally, its purpose. In this case, M-mobile ground installation, P-radar, and Q-intended for a combination of purposes. The figure indicates the model number in the developmental history of the equipment. Developed and hand built after World War II by Marines under Major Marion C. Dalby at the Naval Air Materiel Test Center, Point Mugu, California, the MPQ-14 was first used in Korea in September 1951. Initially, considerable mechanical difficulty was experienced with radar bombing, which affected the accuracy of the bombs, but later the system became sufficiently reliable to permit bomb drops within one mile of friendly lines. Subsequent use confirmed the tactical precision of the MPQ-14. By the middle of summer 1952, the Marines had obtained Fifth Air Force permission to use radar bombing, controlled by a forward observer on the ground, in a close support role.