Some of the enemy ground pressure against the outposts in September and October had been relieved by the increase in the number of air strikes received by the 1st Marine Division. De-emphasis of the Air Force interdiction strategy in favor of striking the enemy wherever (and whenever) it hurt him most had made available more aircraft for close support of ground operations.[233] The UN commander, General Clark, who had given the green light to the shift in USAF policy and targets, followed the giant hydroelectric strike in June with a mass attack the next month on 30 military targets located near the North Korean Capital. During a year’s freedom from air attack (July 1951-July 1952) Pyongyang had become not only the major logistics center for combat equipment and personnel but also the focal point for command and control of Communist ground and air defense efforts. [233] The 1st MAW chief of staff during this period, then Colonel Samuel S. Jack, offered the opinion that “the Fifth Air Force was most sympathetic to Division requirements for close air support from Wing sources. The Eighth Army in the Joint Operations Center proved to be the principal limiting factor in the assignment of air in accordance with these requests. Also, requirements that Division CAS requests filter through I Corps and JOC constituted a major factor in Wing response.” _Jack ltr._ Designated Operation PRESSURE PUMP, the 11 July strike against Pyongyang called for three separate attacks during daylight and a fourth at night. This extended time over the target would give enemy fighters more than ample time to take to the skies in defense of the Capital. Because Pyongyang “was defended by 48 guns and more than 100 automatic weapons, making it one of the worst ‘flak traps’ in Korea,”[234] there was considerable hazard in the operation. Added danger to the pilots resulted from the decision to forewarn the North Korean civilian population of the air assault. General Clark explained the reason for dropping warning leaflets prior to the attack on Pyongyang: [234] Futrell, _USAF, Korea_, p. 482. The objective was in part humanitarian and in part practical. We had to hit Pyongyang because the Communists had made it a major military headquarters and stockpile area. We wanted to warn the people away from danger areas. By warning them away we disrupted their daily lives and made it difficult for the Communists to maintain any kind of schedules in their work in the city.[235] [235] Clark, _Danube to Yalu_, pp. 208–209. Results indicated that both the destructive and the psychological aspects of the mission were successful. American, British, and ROK planes completely destroyed 3 of the 30 military targets attacked. Of the rest, only two escaped major damage: