On 27 May 1944 MacAuthur's 7th Army invaded the island of Biak off the northeast coast of New Gueina. Expecting no more than 2,000 defenders and light resistance the US ran into a much larger and very experianced force of defenders numbering about 10,000 men.
The Imperial High Command at first wrote off the island as a lost cause. But, because of the resolute defense mounted by Colonel Naoyuki Kuzme and R. Adm. Sadatoshi Senda they decided belatedly to reinforce the island and try and hold it.
This what if assumes that the Japanese right from the start decide to hold Biak. Their reasoning being that is a stepping stone and real threat to the Philippines and their supply lines from Indonesia.

US forces on the island consisted of two regiments of the 41st Infantry Division, the 186th and 162nd along with the 542nd Engineering Boat and Shore Regiment along with a company of tanks and other small service and support units.
At sea, the US has available the cruisers Phoenix, Nashville, Boise, and Australia along with 14 US destroyers (mostly Fletcher class) and two Australian DD's, Arunta and Warramunga.

The Japanese land forces on Biak consisted of the 222nd Regiment, a long term China veteran unit of regulars, an aviation engineer battalion and a Special base force of IJN troops. They too have about a company of tanks and small service and support units available. There are 4 4.7" DP coast defense guns and an older 6" coast defense gun in addition.
The Japanese relief force for this scenario (taken from the aborted attempts originally made) are an infantry division loaded on an LST, several transport ships and, four destroyers. Covering this force are the battleships Fuso, Yamato, and Mushasi, heavy cruisers Aoba, Kinugasa, Myoko, and Haguro, the light cruiser Noshiro, and 8 destroyers along with two minelayers.

Both sides have about 200 aircraft of various types available for operations. The Japanese have Zeros and the G4M for offensive operations along with a few flying boats. These are flying out the Southern Philippines. The US 13th and 5th Air Forces are flying P-38, A-20, B-25 and, B-24 along with USN PBY patrol aircraft.

Given that the US is simultaneously making landings on Saipan and about to engage the Japanese carrier fleet in the Philippine Sea battle (Marianas Turkey Shoot) the USN is unable to reinforce the above forces.

I think that the Japanese have an excellent chance to actually make a forced landing of their reinforcements on Biak if they act promptly and in force as outlined above. Much would hinge on the ability of the limited Allied naval forces to engage the Japanese convoy at sea. The same is true of their air forces.
The Japanese also have a reasonable capacity to attack the Allied ships with air power if they try and interviene.
For once, the Japanese actually have material superiority over the Allies. Comments?

__________________
Truth is stranger than bullshit!