Complex sentence: The French immediately received'a shower of balls' from the Chickasaw fortifications, the mantelets proved to be ineffective, and the attack became pinned down on the side of the hill with steadily mounting casualties.
Split into simpler sentences: The French immediately received'a shower of balls' from the Chickasaw fortifications, and the mantelets proved to be ineffective. The attack became pinned down on the side of the hill with steadily mounting casualties.