Complex sentence: Another Scout-Sniper Platoon from the 8th Marines assisted in the main assault landing on D-Day, while the Company D (Scouts), 2nd Tank Battalion worked extensively in the seizure and occupation of other islands in the Tarawa Atoll.
Split into simpler sentences: Another Scout-Sniper Platoon from 8th Marines assisted in the main assault landing on D-Day. The Company D (Scouts), 2nd Tank Battalion worked extensively in the seizure and occupation of other islands in the Tarawa Atoll.