by Philippine Scout engineers on January 1. The Japanese realized the full extent of MacArthur's plan on December 30 and ordered the 48th Division to press forward and seal off Bataan. In a series of actions between January 2 and 4, the 11th and 21st Divisions of the Philippine Army, the 26th Cavalry (PS) and the American M3 Stuart tanks of the Provisional Tank Group held open the road from San Fernando to Dinalupihan at the neck of the peninsula for the retreating forces of the South Luzon Force, then made good their own escape. Despite 50% losses in the 194th Tank Battalion during the retreat, the Stuarts and a supporting battery of 75mm SPM halftracks repeatedly stopped Japanese thrusts and were the final units to enter Bataan. On December 30, the American 31st Infantry moved to the vicinity of Dalton Pass to cover the flanks of troops withdrawing from central and southern Luzon, while other units of the Philippine Division organized positions at Bataan. The 31st Infantry then moved to a defensive position on the west side of the Olongapo-Manila road, near Layac Junction—at the neck of Bataan Peninsula—on January 5, 1942. The junction was given up on January 6, but the withdrawal to Bataan was successful. Battle of Bataan From January 7 to 14, 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 The Japanese 5th Air group was withdrawn from operations on January 5 in preparation for movement with the 48th Division to the Netherlands East Indies.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 January 16. This failed, and the division withdrew to the Reserve Battle Line from Casa Pilar to Bagac in the center of the peninsula on January 26. The 14th Army renewed its attacks on January 23 with an attempted amphibious landing behind the lines by a battalion of the 16th Division, then with general attacks beginning January 27 along the battle line. The amphibious landing was disrupted by a PT boat and contained in brutally dense jungle by ad hoc units made up of