Due to heavy shipping losses earlier in the year during the Battle of the Bismarck Sea , they employed a small force of submarines in an effort to avoid Allied air attack .
The Japanese also relied upon water transport for logistics during the battle .
Due to heavy shipping losses earlier in the year during the Battle of the Bismarck Sea , Japanese employed a small force of submarines in an effort to avoid Allied air attack .
The Japanese also relied upon water transport for logistics during the battle .