Complex sentence: With French help, the incumbent Blaise Compaoré seized power in a coup d'état in 1987, betraying his long-time friend and ally Thomas Sankara, who was killed in the coup.
Split into simpler sentences: With French help, Blaise Compaoré seized power in a coup d'état in 1987. He overthrew his long-time friend and ally Thomas Sankara, who was killed in the coup.