On 23 March, a Chinese Communist regiment attempted to capture three outposts manned by the U.S. 7th Division, at the far right of the I Corps line. Hills 225 (Pork Chop Hill) and 191 held. The enemy’s main effort was against Hill 266 (Old Baldy), defended by units of the division’s Colombian battalion. One attack carried the position, despite company strength reinforcements of the original defenders. Two strong UN counterattacks the next day to retake the outpost failed, and the Chinese retained the crest of Old Baldy. Although the CCF had gained their objective in Hill 266, the battles on the three hillocks had cost the enemy 750 casualties, according to 7th Division records. In one respect, the nature and extent of ground operations affected the type of air activity over North and South Korea during the winter of 1952–1953. Introduction of PRESSURE strategy, which had embodied the policy of the Far East Air Forces since mid-1952, brought more aircraft in close support of Eighth Army ground troops, a change that pleased the corps commanders. When the heavy outpost fighting throughout October diminished to only occasional skirmishes in November, there was temporarily a decreased need for large numbers of CAS sorties. As a result more planes became available for PRESSURE attacks. These strikes at first appeared to be reverting to the previous STRANGLE strategy since railroads were often the targets. But interdiction of the transportation system was only part of the PRESSURE aerial concept which also called for striking enemy production, repair, and storage facilities. The Allied strategy in conducting its air offensive remained the same: to make the bombing hurt the Communists so that they would end their deliberate delaying tactics in the truce sessions and join the UNC in effecting a Korean settlement. During the winter FEAF maintained a steady air pressure against the Communists. Major raids were made from time to time, but the number of strategic targets was gradually disappearing due to repeated UNC air attacks. Further, much of the enemy logistical net had gone so deeply underground during the prolonged stalemate that UN bombing and rocket attacks were having only a limited destructive effect. The U.S. B-29s, which had carried the fight to the enemy since the first week of the Korean conflict, found their last worthwhile objectives in stockpiles hidden in North Korean towns and villages. For the Fifth Air Force fighters there was little opportunity to increase their skill in air-to-air combat, since the Communist fliers continued to take evasive action and avoid “dogfights.”