This Week on History Happy Hour: How did the United States become a superpower? Author and historian David Nasca credits a small group of military mavericks, innovators, and crackpots who defied convention wisdom to develop a unique brand of amphibious warfare that proved critical in winning WWII. Host historians Rick Beyer and Chris Anderson talk to Nasca about his new book "The Emergence of American Amphibious Warfare, 1898–1945." How it helped the US achieve geopolitical supremacy – and why they might be the key to the future. Sunday at 4PM ET on History Happy Hour, the spot where history is always on tap.