Complex sentence: Two groups moved north along both sides of the Raritan River, while a third contingent crossed the river further up to attack from the West, and the fourth group moved from the East to cut the potential retreat route of the Americans.
Split into simpler sentences: Two groups moved north along both sides of the Raritan River, while a third contingent crossed the river further upstream to attack from the west. The fourth group moved from the east to cut the potential retreat route of the Americans.