As the 7th Marines moved to its mission, the 5th Marines was again successfully opening up opportunities on Peleliu’s eastern, “lobster claw” peninsula. Most of those opportunities, unfortunately were never exploited.

By the end of D plus 2, the 5th Marines stood at the approach to the eastern peninsula, and astride the East Road just east of the 1st Marines’ terrible struggle in Umurbrogol. It had fought somewhat clear of the galling fires from Umurbrogol, and planned an assault on the eastern peninsula across a narrow causeway, which the Japanese should certainly defend. Then a D plus 3 reconnaissance of the causeway revealed that the causeway was not defended. The 2d Battalion hastened to seize the opportunity and moved across in strength. The attack was hit by its own supporting fires. The forward battalion CP group was strafed by Navy planes and then hit by artillery airburst, causing the loss of 18 battalion headquarters personnel to “friendly fire.”

Nevertheless, a bridgehead across the causeway was well established on D plus 3, and the 5th Marines’ Colonel Harris moved to exploit it. During the afternoon, he thinned his forces holding the East Road sector, gave the former 3/5 mission to Company L, 3/5, and gave the remainder of 3/5 a new mission. He ordered Gustafson into a position within the bridgehead established by 2/5, and further ordered both battalions then to capture and clear the eastern peninsula. Earlier he had expected such an attack to be against the strong defending forces originally reported on the eastern peninsula. However, the apparent reduction of defending forces now appeared to offer an opportunity to seize Purple Beach quickly, a logistic prize of some significance. Harris knew that the division would need to shift its logistical axis to Purple Beach, away from the fire from Umurbrogol, and away from the threat of westerly storms.

Before dark, Gustafson moved two of his 3/5 companies across the causeway, and moved his own CP group in with the 2/5 CP, where the two commanders jointly planned the next day’s advance. Hoping for little resistance, they directed rapid movement, but armed their point units with war dog sections to guard against ambush. Their lead companies moved out just after dawn. In the 3/5 sector, there was an ambush, but the war dogs warned of, and effectively thwarted, the attempted surprise.

By the end of D plus 4, the two battalions had cleared the main body of the eastern peninsula and had reached Purple Beach from the rear. The defenses were most impressive, but many were unmanned. Those enemy troops encountered seemed more interested in hiding than in fighting, leading to speculation that Nakagawa’s trained infantry had been moved west to the fight on D-Day and/or D plus 1. By D plus 5, Purple Beach was cleared, as were the long peninsulas southwest and northeast of Purple Beach. On D plus 6, 2/5 seized the two islands immediately north of the northeast peninsula, and the next day occupied the small unnamed islet just 1,000 yards east of the northern ridges of Peleliu.

From that position, and positions elsewhere on the other islands, and near Ngardololok, there appeared to be many opportunities to attack by fire against the cave-infested north-south ridges of central and northern Peleliu. Such positioning of heavy weapons would be very difficult, but relative to the intense infantry battles underway in Umurbrogol, such difficulties seemed acceptable. Many of the prospective targets could have been vulnerable to direct, flat trajectory fire across the front of U.S. units advancing north in central Peleliu. Corps artillery units had conducted such direct fire training before embarking for the Peleliu campaign. Such tactical advantages and opportunities from the eastern peninsula were advocated but never exploited. Only later, in the fighting for northern Peleliu was the 5th Marines able to secure point-blank, heavy, single-gun fire support.