Complex sentence: On 29 August 1942, during the Battle of Isurava, Kingsbury, who was one of the few survivors of a platoon which had been overrun by the Japanese, immediately volunteered to join a different platoon which had been ordered to counterattack.
Split into simpler sentences: On 29 August 1942, during the Battle of Isurava, Kingsbury was one of the few survivors of a platoon that had been overrun by the Japanese. He immediately volunteered to join a different platoon, which had been ordered to counterattack.