Complex sentence: Over the 26 days the battle for Iwo Jima waged on, NCB 133 endured 245 casualties, including 3 officers and 39 enlisted killed in action plus 2 MIA, which was the highest number of casualties for any Seabee unit in history.
Split into simpler sentences: Over the 26 days the battle for Iwo Jima waged on, NCB 133 endured 245 casualties, including 3 officers and 39 enlisted killed in action plus 2 mia. This was the highest number of casualties for any Seabee unit in history.