Even after General Geiger had ordered General Rupertus on 21 September to stand down Puller’s shattered 1st Marines, General Rupertus expressed the belief that his Marines, alone, would shortly clear the entire island. After taking a closer look at the situation on the ground, Geiger ordered RCT 321 from Angaur and attached it to the Marine division. Encirclement of the Umurbrogol Pocket now became tactically feasible.
Capture of northern Peleliu and Ngesebus became more pressing with the discovery on 23 September that some part of the enemy’s substantial troop strength in the northern Palaus was being infiltrated by barge from Koror and Babelthuap into northern Peleliu.
Although the naval patrol set to protect against just that reinforcing action had discovered and destroyed some of the Japanese barges, most enemy troops seemed to have waded ashore on the early morning of 23 September. Colonel Nakagawa suddenly had reinforcements in the form of a partially mauled infantry battalion in northern Peleliu.
Encirclement of Umurbrogol and Seizure of Northern Peleliu
A plan to encircle the Pocket, and deny reinforcement to northern Peleliu was immediately formulated. General Rupertus’ staff was closely attended by selected III Corps staff officers, and General Geiger also was present.
The plan called for two regiments to move up the West Road, the Army 321st Infantry leading in the attack, and the 5th Marines following. The Marines were to pass through the Army unit after it had gone beyond the Pocket on its right, and the 5th would continue then to take northern Peleliu and Ngesebus.
COMMITMENT OF
RCT 321, 24 SEPT.
The 321st RCT, by now battle tested, was tasked to push up the West Road, alongside and just atop the western edge of coral uplift which marked the topographical boundary between the flat western plain, and the uplifted coral “plateau.” That plateau, about 300 yards west to east, constituted the western shoulder of the Pocket. The plateau rose some 30–80 feet above the West Road. Its western edge, or “cliff,” was a jumble of knobs and small ridges which dominated the West Road, and would have to be seized and cleared to permit unharrassed use of the road.