Rostow worked in the Office of Strategic Services during World War II and later was a foreign policy adviser and speechwriter for presidential candidate and then President John F. Kennedy; he is often credited with writing Kennedy's famous "New Frontier" speech. Prominent for his role in the shaping of US foreign policy in Southeast Asia during the 1960s, he was a staunch anti-communist, noted for a belief in the efficacy of capitalism and free enterprise, strongly supporting US involvement in the Vietnam War. Rostow is known for his book "The Stages of Economic Growth: A Non-Communist Manifesto" (1960), which was used in several fields of social science. Rostow's theories were embraced by many officials in both the Kennedy and Johnson administrations as a possible counter to the increasing popularity of communism in Asia, Africa and Latin America.