Complex sentence: The campaign season for 1757 had been a successful one for authorities in New France, as the British had a failed expedition against Louisbourg, and were handed a defeat at Fort William Henry at the hands of the French and their Indian allies.
Split into simpler sentences: The campaign season for 1757 had been a successful one for authorities in New France. The British had a failed expedition against Louisbourg, and were handed a defeat at Fort William Henry at by the French and their Indian allies.