In this area, the 5th Marines found flat ground, some open and some covered with palm trees. The ground was broken by the familiar limestone ridges, but with the critical tactical difference that most of the ridges stood alone. Attackers were not always exposed to flanking fires from mutually supporting defenses in adjacent and/or parallel ridges, as in the Umurbrogol. The Japanese had prepared the northern ridges for defense as thoroughly as they had done in the Umurbrogol, with extensive tunnels and concealed gun positions. However, the positions could be attacked individually with deliberate tank, flamethrower, and demolition tactics. Further, it developed that the defenders were not all trained infantrymen; many were from naval construction units.
On the U.S. side of the fight, a weighty command factor shaped the campaign into northern Peleliu. Colonel Harold D. “Bucky” Harris was determined to develop all available firepower fully before sending his infantry into assault. His aerial reconnaissance earlier had acquainted him with an understanding of the terrain. This knowledge strengthened his resolve to continue using all available firepower and employing deliberate tactics as he pursued his regiment’s assigned missions.
On the afternoon of 25 September, 1/5 seized the Radio Station complex, and the near portion of a hill commanding it. When 3/5 arrived, it was directed to seize the next high ground to the east of 1/5’s position. Then when 2/5 closed, it tied in to the right of 3/5’s position, and extended the regimental line back to the beach. This effectively broke contact with the 321st operations to the south, but fulfilled Colonel Harris’ plans to advance north as rapidly as possible, without over-extending his lines. By suddenly establishing this regimental “beachhead,” the 5th Marines had surprised the defenders with strong forces challenging the cave defenses, and in position to engage them fully on the next day.
The following day, 26 September, as the 321st launched its three-pronged attack against Hill 100/Hill B (northern cap of the Umurbrogol Pocket) and the 5th Marines attacked four hills running east to west across Peleliu, dubbed Hills 1, 2, 3, and Radar Hill in Hill Row. The row was perpendicular to and south of the last northern ridge, Amiangal Mountain. These hills and the ridge were defended by some 1,500 infantry, artillerymen, naval engineers, and the shot-up reinforcing infantry battalion which landed the night of 23 September, in caves and interconnected tunnels within the ridge and the hills. As the fight for Hill Row developed, Colonel Harris had his 2d Battalion side-step west of Hill Row and begin an attack on the Amiangal ridge to the north. Before dark, the 2d Battalion had taken the southern end and crest of the ridge, but was under severe fire from cave positions in the central and northwestern slopes of the ridge.