Complex sentence: At his death the alliance between the French and the Natchez became unstable as the leaders of the pro-English White Apple village gained influence, which eventually led to the Natchez Massacre of 1729, and the end of amiable relations between the French and the Natchez.
Split into simpler sentences: At his death the alliance between the French and the Natchez became unstable as the leaders of the pro-English White Apple village gained influence. This eventually led to the Natchez Massacre of 1729, and the end of amiable relations between the French and the Natchez.