During WWII, what did researches discover when comparing amphetamines to caffeine?

During WWII, what did researches discover when comparing amphetamines to caffeine?

Nicolas Rasmussen (Professor of History and Philosophy) gives expert video advice on: How did amphetamine become methamphetamine?; How was the German Blitzkrieg influenced by amphetamines during World War II?; Why did the German army cut back on amphetamine use? and more...