Complex sentence: During World War II, the original regiments of the 101st Airborne Division painted a suit from a deck of cards on their helmets to denote the division's four infantry regiments.
Split into simpler sentences: During World War II, the 101st Airborne Division undertook steps to identify paratroopers from each divisional element visually. As a result, a suit from a deck of cards was painted on the helmets of the division's four infantry regiments.