America's U-BoatsThe submarine was one of the most revolutionary weapons of World War I, inciting both terror and fascination for militaries and civilians alike. During the war, after U boats sank the Lusitania and began daring attacks on shipping vessels off the East Coast, the American press dubbed these weapons Hun Devil Boats, Sea Thugs, and Baby Killers. But at the conflicts conclusion, the U. S. Navy acquired six U boats to study and to serve as war souvenirs.