Complex sentence: The August 29th Movement (or August Twenty-Ninth Movement, ATM), was a Chicano communist organization that lasted from 1974 to 1978, the first US Marxist Leninist organization that originated outside the White Left.
Split into simpler sentences: The August 29th Movement (or August Twenty-Ninth Movement, ATM), was a Chicano communist organization that lasted from 1974 to 1978. It was the first United States Marxist-Leninist organization that originated outside the White Left.