From 7 to 14 January 1942, the Japanese concentrated on reconnaissance and preparations for an attack on the Main Battle Line from Abucay to Mount Natib to Mauban. At the same time, in a critical mistake, they also relieved the 48th Division, responsible for much of the success of Japanese operations, with the much less-capable 65th Brigade, intended as a garrison force. The Japanese 5th Air group was withdrawn from operations on 5 January in preparation for movement with the 48th Division to the Netherlands East Indies. U.S. and Filipino forces repelled night attacks near Abucay, and elements of the U.S. Philippine Division counterattacked on 16 January. This failed, and the division withdrew to the Reserve Battle Line from Casa Pilar to Bagac in the center of the peninsula on 26 January.