Complex sentence: When Cornwallis occupied Yorktown, the Legion was posted across the York River at Gloucester, fought a skirmish with French troops there, and surrendered to the French at the conclusion of the siege.
Split into simpler sentences: When Cornwallis occupied Yorktown, the Legion was posted across the York River at Gloucester. It later fought a skirmish with French troops there and surrendered to the French at the conclusion of the siege.