Complex sentence: As the conflict between the American forces and the Communists in Vietnam escalated throughout the 1960s, Fall became increasingly pessimistic about the U.S. 's chances of success, predicting that if it did not learn from France's mistakes, it too would fail in Vietnam.
Split into simpler sentences: As the conflict between the American forces and the Communists in Vietnam escalated throughout the 1960s, Fall became increasingly pessimistic about the U.S. 's chances of success. He predicted that if it did not learn from France's mistakes, it too would fail in Vietnam.