The raider headquarters and both Marine battalions embarked in
transports on 28 August and sailed for Guadalcanal. The New Georgia
campaign had been a costly one. Each raider battalion had suffered
battle casualties of more than 25 percent. In addition, sickness had
claimed an even greater number. The 1st Raiders now had just 245
effectives; the 4th Raiders only 154.
_Bougainville_
In the immediate aftermath of the fall of New Georgia, the Allies
seized other islands in the vicinity, to include Arundel, Vella
Lavella, and Kolombangara. Thereafter the South Pacific command turned
its attention to the next major step in the encirclement of Rabaul.
There were several options, but the final choice was a landing on
Bougainville, the largest island in the Solomons group. A month later
MacArthur’s command would assault Cape Gloucester on the western end
of New Britain. Rabaul would then be within range of Allied land-based
fighter aircraft coming from two directions. Air power thus could
neutralize the Japanese bastion and allow it to be by-passed. The
scheduled D-day for Bougainville was 1 November 1943.
[Illustration: _Cape Torokina on Bougainville is seen after the Allies
built an airstrip. Threatening Puruata Island, assaulted by the 3d
Raider Battalion on 1 November 1943, is in the foreground. Tiny
Torokina Island lies in between Puruata and the Cape._
Department of Defense Photo (USMC) 68047
]
Several factors dictated Halsey’s scheme of maneuver for the offensive.
First, he had too few transports and Marines to make a direct assault
on the heavily defended enemy airfields located on the northern and
southern ends of the island. Another consideration was the range of
land-based fighters from bases in the Central Solomons--they could only
effectively cover a landing in the southern half of Bougainville. The
planners settled on the Empress Augusta Bay-Cape Torokina region on
the western side of the island. Defenses were negligible there, and
Bougainville’s difficult terrain would prevent any rapid reaction from
enemy ground forces located elsewhere on the island. Once ashore, the
invasion force would seize a defensible perimeter, build an airfield,
and eventually neutralize the remainder of the island from this
enclave. A patrol landed by submarine in late September discovered
that the areas back of the landing beaches were swampy. Aerial
reconnaissance in October also discovered the construction of new
defenses. Neither of these facts changed the plan, however.
[Illustration: I MARINE AMPHIBIOUS CORPS