Complex sentence: They then proceed through the Japanese underground tunnels to attack the artillery-filled Point, one of the major Japanese strongholds that had destroyed many landing boats when they first landed, allowing American ships to advance, and the island of Peleliu finally falls into American hands.
Split into simpler sentences: They then proceed through the Japanese underground tunnels to attack the artillery-filled Point, one of the major Japanese strongholds that had destroyed many landing boats when they first landed. This allows American ships to advance, and the island of Peleliu finally falls into American hands.