This, the first of two volumes on Germany's World War II U-boats, traces their development from the early U-boats of the Kaiser's Navy, the prohibition on Germany having U-boats following the Armistice in 1918 and the subsequent Treaty of Versailles, the secret development of U-boats using a 'cover-firm' in Holland, culminating in the formation of the 1st U-boat Flotilla in 1935 with the modern Type II.