Complex sentence: In early 1944, Barrowclough commanded a force of nearly 16,500 men during the Battle of the Green Islands, only a third of which were elements of his own division.
Split into simpler sentences: In early 1944, Barrowclough participated in the Battle of the Green Islands. During this battle, he commanded a force of nearly 16,500 men, only a third of which were elements of his own division.