Dönitz, Karl (1891–1980) (1919) forbade Germany from building or operating any U-boats Dönitz emerged from the Great War as perhaps the world’s most accomplished student of submarine warfare He was the obvious person to head a secret planning group within the Kriegsmarine, which spent the 1920s in U-boat research and planning, using front companies located in Denmark and the Netherlands Nine training boats were thus already built in secret and serviceable when the Anglo-German Naval Agreement lifted the U-boat ban in 1935 Dönitz oversaw construction of an expanded U-boat fleet leading into the war, though he failed to make his view prevail with Adolf Hitler that U-boats would be the main challengers to British sea power in the event of war Well before the war Dönitz envisioned a navy made up primarily of U-boats, supported by air reconnaissance and naval intelligence But, until 1943, Hitler remained committed to the ill-timed and even fantastical Z-Plan He was also held back during most of the prewar period by the parity clause of the 1935 agreement, which limited German U-boats to the same tonnage as submarines of the Royal Navy He therefore opposed plans to build “U-cruisers” or super U-boats, as these took up too much of the permitted tonnage From the start of the Battle of the Atlantic (1939–1945), Dönitz was the most important figure in the Kriegsmarine, personally directing all U-boat operations When the United States fully entered the fight in December 1941, Dönitz promised Hitler “einen kräftigen Paukenschlag” (“a mighty drumroll”) of U-boat sinkings off the American coast His captains did indeed enjoy their second “happy time” of the war, but Dönitz was held back by Hitler’s insistence on deploying U-boats to defend iron ore supplies from Sweden that passed through Norwegian waters, while others were diverted into new campaigns in the Mediterranean Dönitz replaced Admiral Erich Raeder as commander in chief of the Kriegsmarine on January 30, 1943, and immediately ordered a halt to construction of capital warships He transferred all work and combat crews to submarines, thereby finally achieving his dream of a vast submarine fleet of at least 300 U-boats Organized to fight in wolf packs to hunt down and mass attack convoys, it was already too late: Dönitz’s U-boats lost the battle that summer He recalled all boats from the deep Atlantic and ordered them to prowl only in coastal waters A fanatic Nazi and fierce anti-Semite, after failure of the July Plot Dönitz broke with German military tradition and joined the Nazi Party in 1944 He was named Hitler’s successor on April 30, 1945, after spending many of the final days with his lord and master deep underground in the Führerbunker in Berlin Upon Hitler’s suicide, Dönitz was briefly the last Führer of the Third Reich His signature act as leader was to order Operation REGENBOGEN Then he formally surrendered all German armed forces to the Allies He was retained for two weeks by the Allies to assist with physical surrender of German ground forces, then arrested He was tried by the Nuremberg Tribunal as a major war criminal, largely on the insistence of Soviet and British authorities He was acquitted of crimes against peace and against humanity, but convicted of palling a war of aggression He was also charged with war crimes for orders to U-boat captains to ignore rules of cruiser warfare specified under the London Submarine Agreement (1936), notably explicit instructions not to rescue enemy or neutral crew and passengers from any ships sunk A specific 319