Complex sentence: Most were of aviation or Japanese and Korean labor units who had little or no combat training and were not assigned weapons or a battle station, and the number of trained combat troops on Makin was no more than 300 soldiers.
Split into simpler sentences: Most were of aviation or Japanese and Korean labor units who had little or no combat training and were not assigned weapons or a battle station. The number of trained combat troops on Makin was no more than 300 soldiers.