So what happenned?
To put it simply, it wasn’t a war-winning weapon. Worse for Germany, it didn’t really do anything … and arguably hastened the Third Reich’s defeat. For one, the submarines—only two were ever operational—suffered from several technical problems that forced engineers to work overtime to resolve. The hydraulic torpedo loading systems didn’t work at first. The engines and steering systems were defective. This made the submarines “decidedly less of a threat than originally foreseen,” Jones writes.
On May 4, 1945 one of the most advanced submarines in the world crept up to a British Royal Navy cruiser. U-2511 was one of Germany’s new Type XXI-class “wonder” submarines, and she was hunting for Allied ships.
She also represented one of the Third Reich’s biggest failures.
More than 250 feet long and displacing 1,620 tons, the Type XXI packed six hydraulically-reloaded torpedo tubes capable of firing more than 23 stored torpedoes. This arsenal could turn a convoy into sinking, burning wreckage.
But the real improvement lay deep inside the U-boat’s bowels. There rested an advanced electric-drive engine that allowed the submersible to travel underwater at significantly higher speeds—and for longer periods—than any submarine that came before.
It was perhaps the world’s first truly modern undersea warship. The engine, which was radical for its time, allowed the boat to operate primarily submerged. This is in contrast to other war-era submersibles, which operated mainly on the surface and dived for short periods to attack or escape.
But for the fortunate crew of that British cruiser, the war in Europe had just ended. Adolf Hitler shot himself on April 30. Word of the European ceasefire had also just reached U-2511. The submarine did not fire its torpedoes at the cruiser, instead merely carrying out a mock practice attack.
Neither U-2511 nor its sister ship U-3008 ever fired a torpedo in anger during the war. But the Kriegsmarine—the Nazi navy—had put its hopes in winning the naval war on these Type XXI U-boats.
What went wrong, and the lessons learned from the submarine program, is also the subject of new research. It was featured in Adam Tooze’s 2006 book The Wages of Destruction: The Making and Breaking of the Nazi German Economy  as an example of what not to do.
Now in a recent article  for the quarterly Naval War College Review, Marcus Jones—an associate professor at the U.S. Naval Academy—describes the submarine as one of the preeminent examples of Germany’s “irrational faith in technology to prevail in operationally or strategically complex and desperate situations.”
Desperation fuels innovation
The Type XXI project dates to 1943. Germany was well into a submarine war in the Atlantic, and aimed to choke and starve the United Kingdom from its colonies.
Germany’s goal was to surround the British isles with hundreds of submarines, preventing anything from getting in or out. Initially, this was successful. In October 1942 alone, U-boats sank 56 ships … and that was just in the passage between Iceland and Greenland.
But these successes turned badly against Germany—and fast. By 1943, new convoy tactics, radar and anti-submarine patrol planes caused serious problems with Germany’s predominantly Type VII submarines.
Germany’s existing submarines were now vulnerable to being detected and sunk in huge numbers. Their electric engines—used when underwater and recharged with diesel on the surface—were not capable of holding a charge lasting more than a few hours.
And they were slow. Really slow. Many convoys could simply outrun them. If the Allies detected a sub lurking underwater, they could simply wait it out. In May 1943 alone, the Allies destroyed 43 U-boats, or 25 percent of Germany’s entire operational submarine strength.
At this point, Hitler and Germany’s senior military commanders realized that “no amount of willpower or doctrinal ingenuity on the basis of existing boat types could overcome the collective effects of the countermeasures the Allies employed so well by 1943,” Jones writes.
The result was building a new kind of submarine that—in theory—would fundamentally change the nature of the war at sea.
Designed by propulsion engineer Helmuth Walter, the Type XXI had a unique figure-eight interior which allowed for a significantly larger electric battery. It only had to surface rarely surface and recharge its battery with conventional diesel fuel.
It was also fast enough to keep up with convoys. It could run silent for 60 hours at five knots. It could also pick up the pace, traveling for an hour and a half at a breakneck speed of 18 knots. By contrast the Type VII could not travel faster than eight knots underwater—and then only for short periods.
As Jones points out, the new design also included “sensors, countermeasures, and other devices understood to be indispensable in the commerce war.” These devices included active radar and sonar and a more advanced passive sonar to pick up the sounds of enemy ships.
But everything about the Type XXI was a mistake.
To put it simply, it wasn’t a war-winning weapon. Worse for Germany, it didn’t really do anything … and arguably hastened the Third Reich’s defeat.
For one, the submarines—only two were ever operational—suffered from several technical problems that forced engineers to work overtime to resolve. The hydraulic torpedo loading systems didn’t work at first. The engines and steering systems were defective. This made the submarines “decidedly less of a threat than originally foreseen,” Jones writes.
Germany largely ironed out these problems. But even if the submarines had worked perfectly at the outset, it’s unlikely they would have had much of an effect on the outcome of the war.
This is because the submarines were tied to a losing strategy. And in 1945, German naval strategy was a hopeless cause.
Navies expect their submarine commanders to operate independently. But a mission as huge as stopping shipping across the Atlantic takes much more than submarines. The Germans had a severe shortage of both maritime patrol planes and air bases. In the harsh, rough seas and stormy weather of the North Atlantic, this meant the Germans were limited by what they could hear and see from their U-boats.
By comparison, Allied patrol planes were hunting them.
While technologically advanced for its time, the Type XXI still existed before the age of nuclear submarines, cruise missiles and nuclear-tipped ballistic missiles.
These strategic weapons turned Cold War submarines into the truly decisive platforms they are today. Submarines during World War II were used mainly for defending friendly coastlines, harassing enemy warships and interdicting enemy convoys. The Type XXI was meant to carry out these same missions, but simply more effectively.
But in all three areas, Germany had already lost. Germany’s coastlines were under regular attack by Allied bombers. Allied ground armies were already closing in on the Rhine. And Allied convoys were so numerous, Germany would have to build its new submarines by the hundreds to make much of a dent. This was not physically possible.
As Germany’s ports were no longer secure, engineers had to construct the submarines in sections and transport them on a complex system of cranes and barges to their launch points. This made fixing problems—expected on new ship designs—much harder to fix.
Another problem is that putting too much emphasis on wonder weapons distracts from practical war efforts. In terms of steel committed to the project, “the program cost the war effort some five thousand tanks, a very consequential figure, and could be said to have hastened the defeat of Germany on the Eastern Front,” Jones writes.
This mentality amounted to a “disease ” in German war planning, Jones argues. From V1 and V2 rockets, super-heavy Tiger II tanks and jet fighters, Germany built radical weapons that would fail to turn the tide against an inevitable defeat brought about by larger economic, political and technological disadvantages.
As the war turned against Berlin, the Nazi commanders accelerated development of new weapons, which distracted from other areas. Then the war worsened, accelerating new weapon development further in a perverted, vicious cycle.
However, the Type XXI would last through the Cold War. Some were used for target practice. Others were captured and commissioned into the Soviet and French navies. The only surviving vessel of its class today is the Wilhelm Bauer, which the modern Germany navy converted into a research vessel. It’s now a museum ship in Bremerhaven.
But mainly, the Type XXI provides several lessons in how technology—while important—doesn’t alone win wars. It’s also a lesson in how the fanatical pursuit of advanced weapons can make winning wars a lot harder.