Complex sentence: The Chilean right wing believed that Allende was too far to the political left; backed by the United States, who opposed Allende's socialist politics, the right staged a coup d'état on September 11,1973 through the Chilean military, and Death of Salvador Allende.
Split into simpler sentences: The Chilean right wing believed that Allende was too far to the political left. Backed by the United States, which opposed Allende's socialist politics, the right staged a coup d'état on September 11,1973 through the Chilean military, and Death of Salvador Allende.