Complex sentence: More than 20 Japanese were located in a cave on the east side of the peninsula, and killed by members of "E" Troop and personnel from the squadron headquarters; the remaining Japanese units in the area retreated to the east.
Split into simpler sentences: More than 20 Japanese were located in a cave on the east side of the peninsula, and were killed by members of "E" Troop and personnel from the squadron headquarters. The remaining Japanese units in the area retreated to the east.