Taking place on the island of Biak, in Geelvink Bay, in present-day Indonesia, it was part of General Douglas MacArthur's South West Pacific Area's offensive drive to clear New Guinea in preparation for an invasion of the Philippines.

It was the first major effort by the Japanese to allow uncontested landings for the purpose of creating a kill zone inland.

The island of Biak forms part of the Schouten Islands, and dominates the entrance to Geelvink Bay, near the western end of New Guinea; its terrain and location about 325 miles (523 km) from Hollandia and 180 miles (290 km) from Sarmi (where the Japanese had begun concentrating supply bases and airfields), made it well suited to airfield construction, particularly in the flatter southeastern area.

Allied planners considered these beaches to be poorer for landing operations, compared to those further away from the airfields, but they were chosen due to their proximity to the main Allied objectives and because aerial reconnaissance indicated that the beaches were not backed by cliffs or swamps, and that there were two jetties nearby that might facilitate deep-water port access.

[4] The assault force consisted of five destroyer transports (APD), eight LSTs eight LCTs, and fifteen LCIs, supported by a myriad of smaller vessels including DUKWs, LCVPs and LVTs, which were chosen due to concerns about the coral reef opposite the landing beaches.

[7][8] The naval forces, designated Task Group 77.2, were commanded by Rear Admiral William Morrow Fechteler.

Initially, the majority of the combat troops (about 4,000 personnel), were drawn from the veteran 222nd Infantry Regiment which had previously served in China,[3] along with tanks from the IJA 36th Division, supported by artillery, anti-aircraft, construction and naval guard and base troops under Rear Admiral Sadatoshi Senda.

[11] Due to the size of the coastline he had to defend, and based on an appreciation of the Allied objectives, Kuzume focused his defensive plans away from the water's edge.

Instead, he decided to carry out a feint, allowing the Americans to come ashore unopposed so that they would advance into the trap he had prepared for them utilizing a series of caves that were located west of Mokmer and to the east of Bosnek.

This defensive complex was intended to turn the area around the vital airfield into a honeycomb of defended caves and pillboxes filled with riflemen, automatic weapons, artillery, batteries of mortars, and a single company of Type 95 Ha-Go light tanks.

Kuzume also stockpiled these positions with ammunition and other supplies, with several dumps located around the eastern cave area, along with living quarters for the defenders.

[12] Water was limited on Biak and had to be strictly rationed by the US troops, and heat and humidity would take a heavy toll during the fighting.

[14] The invasion force assembled largely in the Humboldt Bay area near Hollandia, and after only limited rehearsals departed late on 25 May.

The Japanese had been seeking to engage the Americans in a decisive battle, the Kantai Kessen, that would enable them to win the war.

A total of 2,500 troops from the 2nd Amphibious Brigade were assigned for transport from Mindanao; they were to be escorted by a force under Rear Admiral Naomasa Sakonju, consisting of the battleship Fuso, the heavy cruisers Aoba, Myoko and Haguro, the light cruiser Kinu, and eight destroyers (five as part of the screen and three as part of the transport element).

[2] The Japanese fought to annihilation, with 4,700 killed and 200 captured; the remainder faced death from disease and starvation in the following months.

Several runways were constructed by US engineers on nearby Owi, while Mokmer Drome was operational by 22 June, and was further improved and expanded with hardstandings for over 100 aircraft throughout July and into August.

These fields were not completed in time for use during operations to capture the Marianas in June, but they were utilized during follow on actions against the Palau Islands in September; Biak was also used to strike targets in Mindanao and in the Netherlands East Indies.

The Battle of Saipan which happened at the same time coincidentally also permanently canceled Operation KON and the battleships that were planning to attack MacArthur's small naval forces consisting of no aircraft carriers or battleships and only a few cruisers and destroyers were ordered north to screen aircraft carriers.