Biak is the largest of the Schouten Islands, located in a large gulf in the north coast of western New Guinea. In 1941, the island had a completely undeveloped anchorage at Mokmer (136.107E 1.189S) and considerable flat ground suitable for airfields.
The Japanese
occupied the island in the spring of 1942 and built an airfield capable
of operating bomber aircraft. MacArthur coveted this
airfield, which was well situated to support Nimitz' landings on the Marianas and Palau. Elements of 41 Division (Fuller) began landing on
27 May 1944 against light opposition and rapidly advanced on
Mokmer airfield.
MacArthur had discounted intelligence showing 11,000 Japanese troops and light tanks on the island. This intelligence was confirmed when the American troops began to close on the airfield. The Japanese defenders (drawn primarily from 222 Infantry Regiment and 28 Naval Base Force) suddenly opened fire from heavily fortified cave positions north of the airfield, then counterattacked from the west in battalion strength. Lead elements of 162 Regiment were forced to withdraw. The next morning, the Japanese counterattack was joined by light tanks. By then the Americans had brought up Sherman medium tanks, which completely outclassed the Japanese machines and were able to cover the withdrawal of 162 Regiment in amtracs.
It took a week for Fuller's division to regroup and take the
airfield. By then MacArthur's patience had run out, and Fuller was
relieved by Eichelberger.
Japanese resistance was not
broken until 28 June, when the fortified caves in the west of the
island were finally reduced. Mopping up continued until 20
August. The Americans suffered 2550 casualties and took 220 prisoners.
During the battle, a Japanese naval radio unit ran into an American
patrol and lost several codebooks.
This prompted the Japanese to make emergency changes in their radio
procedures, which slowed down their communications just as the Battle of the Philippine Sea
was getting under way.
The Japanese high command reacted strongly to the Biak invasion,
which threatened to disrupt plans for a decisive battle in the central
Pacific (A-Go.) The Navy began
concentrating its land-based air power in western New Guinea and
assembled a strong escort force to transport the 2500 men of the Army's
2 Amphibious Brigade to Biak.
But, although the Japanese force included battleship Fuso,
the Japanese retreated when they were discovered by American
reconnaissance planes
and when their own reconnaissance planes
mistakenly reported a fleet
carrier off Biak. Unknown to the Japanese, the American
reconnaissance was directed by Ultra decrypts.
A second attempt to run in reinforcements on landing barges towed by
destroyers was turned back by B-25s and an Allied cruiser-destroyer force. Again,
Ultra decrypts had warned the Allies, who spotted the approaching
Japanese by aircraft and on radar.
The Japanese apparently spotted the Allied force on their own radar,
launched torpedoes, and fled.
Though no hits were inflicted on the Allies, they were unable to catch
the fleeing Japanese force.
Finally, the Japanese assembled an armada that included both Yamato
and Musashi, but this operation was
called off when Spruance
began his landings in the Marianas. It has been suggested that the
Japanese would have done better to stay with their Kon plan, which would probably have
inflicted a serious defeat on the weak American naval forces off Biak,
rather than send the super battleships north to a battle to which they
contributed little.
References
The Pacific War Online Encyclopedia (c) 2007 by Kent G. Budge. Index