Nevertheless, the US troops were able to secure a lodgement from where they subsequently broke out, advancing north as part of a flanking drive on Salamaua, which was launched in conjunction with attacks by Australian forces further west.

In late June and early July, Allied forces were advancing towards Salamaua, having secured the airfield at Wau earlier in the year.

[1] The plan was made following a recommendation from Commander Morton C. Mumma to the Allied South West Pacific Area GHQ that a beachhead at Nassau Bay would greatly shorten the supply line for Australian and American troops fighting in the Salamaua region.

[3] During the night of 28 June, the 162nd Infantry Regiment's Intelligence and Reconnaissance Platoon placed lights upon islands lying offshore between Nassau Bay and Mageri Point to guide the invasion flotilla.

[4] 'D' Company of the Australian 2/6th Infantry Battalion from Lababia Ridge was required to march to the mouth of the Bitoi River to divert Japanese attention from Nassau Bay.

Further afield, the Japanese had established strong posts around the mouth of the Bitoi River and at Cape Dinga, where it was estimated that there were about 375 personnel; in between there were several small outposts.

[9] Prior to the landing B-25s from the US Fifth Air Force bombed Japanese strong points along the Bitoi River, and A-20s pounded a supply dump on the southern side of Nassau Bay on 29 June.

PT boats PT-142, PT-143, and PT-120 of the US Seventh Fleet took aboard 210 men of Lieutenant Colonel Harold Taylor's 1st Battalion, 162nd Infantry Regiment,[12] with PT-68 providing escort.

[14] With rough seas, heavy rain, and poor visibility the landing force lost escort PT-68 after leaving Mort Bay.

The Landing Craft Mechanized, after unloading a bulldozer was able to proceed back out to sea and retrieved the troops off PT 142 and then returned to the beach, where it too began taking on water and became flooded.

[17] The Japanese defending the landing area – consisting of a small six-man observation post[18] – offered a brief defence before fleeing into the jungle, believing according to Miller, "that the bulldozer was a tank".

[12] After a brief engagement with the Japanese, during the first night two US infantry companies – 'A' and 'C' – secured a perimeter around the beachhead, with defensive positions being set up about 300 yards (270 m) north and south of the lodgement.

[12] At dawn on 30 June, beach clearance teams removed stores and equipment, while machine guns from the wrecked landing craft were brought ashore and established around the position to provide fire support to the perimeter.

'A' Company patrolled north to the south arm of the Bitoi River and ran into Japanese mortar and machine gun fire and forward movement stopped.

[22] Around the beachhead, a hastily prepared defensive line was established by an ad hoc force of engineers, Australian infantry, and headquarters personnel.

[29] The Battle of Roosevelt Ridge was subsequently fought between mid-July and mid-August, concurrently with actions to finally capture the village of Mubo and seize Mount Tambu as the Allies sought to draw reinforcements away from Lae, where an amphibious landing was planned for September 1943.