Complex sentence: Washington continually supplied arms to the Shah and the CIA-trained SAVAK, his secret police force; however by the 1979 revolution, his increasingly independent policies resulted in his effective abandonment by his American allies, hastening his downfall.
Split into simpler sentences: Washington continually supplied arms to the Shah and the CIA-trained SAVAK, his secret police force. However by the 1979 revolution, the Shah's increasingly independent policies resulted in his effective abandonment by his American allies, hastening his downfall.