The second position, the D-2 line, extended in general along the arc of the Agno River, one of the formidable natural barriers in the central plain. After holding for one day on this line, the troops were to retire next to the D-3 line, stretching from Santa Ignacia on the west through Gerona and Guimba to San Jose on the east. The D-4 line was approximately twenty-five miles long and extended from Tarlac on the left (west) to Cabanatuan on the right. Small rivers and streams intersected this line, which, at Cabanatuan, was anchored on the Pampanga River.

On the Agno River the Japanese halted to consolidate their position and bring up more troops. During the 27th, artillery, armor, and service troops moved forward to join the 48th Division. The 47th Infantry and a battalion of artillery, in reserve near Pozorrubio since 24 December, together with the 7th Tank Regiment, were dispatched to Tayug. Infantry and artillery units occupied San Quintin to the south and patrols pushed forward into undefended Umingan. On the 48th Division right (west), the 1st Formosa consolidated its hold on Resales. One battalion of the regiment remained at Urdaneta, and another went on to Carmen to relieve Colonel Tanaka's troops who then moved back across the Agno to Villasis for rest.⁵⁰

By 28 December the North Luzon Force was on the D-4 line. In the face of a well-trained and better equipped enemy, it had fulfilled its mission-to hold the Agno line until the night of 26-27 December and to withdraw to the Tarlac-Cabanatuan line.

The term line, applied to the five delaying positions, is misleading. Actually the front was too wide to be held continuously by the forces available to General Wainwright. Unit commanders were given considerable leeway in occupying their positions and usually could do little more than place their troops so as to cover the most likely routes of approach. Each line was to be occupied before dawn, held during the day, and evacuated at night, the troops withdrawing to the next line. Their withdrawal would be covered by a shell, a small part of the retiring force, which was to remain in position until just before dawn when it was to pull back hastily to rejoin its parent unit on the line below. This shell, in theory, would consist of an infantry-artillery team, but in practice often included only one of these arms.