Full transcript
0:00In March 1943, Grand Admiral Dönitz’ U-boats are on the attack – they sink
0:04108 Allied vessels that month alone. Allied officials are desperate,
0:08and some fear a German victory in the Atlantic is imminent. If the Allies lose the Atlantic,
0:14Britain loses its lifeline – and maybe even the war. But by May 1943, it will be the U-boats
0:20limping home in defeat. So how, in just two months, did the U-boats go from hunters to hunted?
0:38From 1939, German U-boats threaten Allied shipping. Although German surface raiders
0:42do play a role, Admiral Karl Dönitz hopes his submarines can wage a so-called ‘tonnage war’
0:48against British merchant vessels. This means sinking enough merchant shipping to either
0:53massively degrade British military capabilities, or better yet – force London to surrender.
1:00At first, the Germans have some success. Dönitz calls summer 1940, “the happy time”,
1:06in which U-boats easily target mostly isolated merchantmen, sinking 471. When the US joins the
1:13war in 1942, this increases to 1,160. The U-boat crews' term this the “second happy
1:22time” or even “American Shooting Season”. For British Prime Minister Winston Churchill,
1:28the Atlantic is the critical theatre on which all others depend, and by
1:32late 1942 it is one of the few areas in which Germany remains decisively on the offensive.
1:38In November 1942, U-boats alone sink 768,000 gross tons of Allied shipping, their peak for the entire
1:46war. As a result, Churchill asks his allies for more assistance. He also lays down new guidelines
1:52for referring to the German submarine threat: “Enemy submarines are to be called U-boats.
1:59The term “submarine” is to be reserved for Allied underwater vessels. U-boats
2:04are those dastardly villains who sink our ships, while submarines are those gallant
2:09and noble craft which sink theirs.” (Gannon) At the Allied Casablanca conference in January
2:161943, US leaders agree to prioritise the Atlantic and delay the invasion of France and
2:21Germany until 1944 . Although some commanders accept reluctantly, others understand it is
2:27impossible to use the United Kingdom as a base for invasion with a lingering U-boat threat.
2:33But even with promises of more US support,
2:35issues remain. Across the allied effort there is significant demand
2:39and internal competition for scant resources. Meanwhile, Dönitz has more U-boats than ever.
2:46In 1939, Dönitz had just 39 subs, but by early 1943 he has around 300 and more are being build.
2:54Then, when Grand Admiral Erich Raeder’s resigns as Navy Commander-in-Chief in January 1943, Hitler
3:00promotes Dönitz to the top naval position . Hitler tells Dönitz to maintain the pressure in the
3:05Atlantic, although the admiral remains realistic about the challenge in a radio broadcast:
3:12“The harsh realities of the submarine war [means that] even more difficult
3:16times lie ahead of us.” (Van der Vat 289) With a submariner in command of the entire German
3:22navy, the Allies also expect the U-boat menace to grow. One area of concern is the Mid-Atlantic Air
3:28Gap, a favoured U-boat hunting ground known to allied seamen as “Torpedo Junction”. By 1943,
3:35partly thanks the massive expansion of the Royal Canadian Navy, Allied warships can provide
3:40end-to-end escort, but they’re still too few and remain vulnerable without air support. Airbases
3:46in the UK, Iceland, US and Canada have been improving coverage, but there’s still a gap of up
3:53to 1,000-km gap off the Cape of Farewell. Allied commanders try to close it with escort carriers
3:59– including retrofitted civilian vessels – or Very Long-Range bombers like the B-24 Liberator,
4:05but until January 1943, British Coastal Command only has 6 VLR Liberators. The majority go to the
4:12bomber offensive against Germany or the Pacific. Meanwhile, in December 1941, the German navy’s
4:18Beobachtungsdienst intelligence service cracked the British Naval Cipher No. 3. By intercepting
4:24British communications, they organise group attacks on convoys. U-boats locate about 70%
4:30of convoys thanks to codebreaking. Allied resources are also drained by
4:34the 1942 Operation Torch landings in North Africa, and the Battle for Tunisia in early
4:401943. The Royal Navy diverts 125 destroyers and other escort ships to Torch, while fuel
4:47demands for African operations mean North Atlantic convoys have less fuel to out-manoeuvre U-boats.
4:53The result is an increase in sinkings in early 1943. In March alone,
4:58German U-boats and surface ships sink 120 Allied ships globally, totalling 704,000
5:05tons – 484,000 of which sinks in the Atlantic. This rapid increase in tonnage sunk – 74% over
5:13the previous month – is often seen as a major crisis. A March 1943 British memorandum claimed:
5:21“...[T]here is insufficient shipping to allow us to develop the offensives against the enemy,
5:25which have been decided on. Every ship sunk makes the situation worse... We can no longer rely on
5:31evading the U-boat packs and, hence, we shall have to fight the convoys through them.” (Haslop 210)
5:38A December 1943 Allied report even goes so far to suggest victory in the Atlantic – and therefore
5:44the entire war - was threatened. More recent research though,
5:48has questioned the crisis idea. The supposed March crisis mostly focuses on two convoys,
5:54which suffer disproportionate losses – 22 of 90 merchant vessels sunk. Overall, however,
6:00only 31% of March convoys are attacked, much lower than the 52% attacked in November 1942. In fact,
6:08in the first quarter of 1943, sinkings are lower than any 1942 quarter. The allies are also
6:14building more ships than they are losing, with a net gain of 2 million gross tons by March 1943.
6:21Perhaps most significantly, there is nothing in German sources which portrays March as a moment
6:26of imminent victory. In fact, within two months, the U-boats withdraw from the Atlantic in defeat.
6:35Just as the March convoy battles are raging, the Allies meet in the Atlantic Convoy Conference
6:40to better pool resources and standardise procedures. The top priority is closing
6:45the mid-Atlantic Air Gap and taking the fight to the U-boats. The Commander-in-Chief of the
6:50Western Approaches is optimistic: “I really have hopes now that we
6:55can turn from the defensive to another and better role – killing them.” (Redford 74)
7:02Early 1943 also sees several tactical, technological and military developments all
7:08coming to fruition around the same time. Ultra intelligence, from the cracked German Enigma
7:13is the most well-known tool available to the Allies, but it was by no means
7:17the only one – or even the most important. Ultra can provide a general location of most
7:23U-boats, which are tracked by the men and women in London’s Submarine Tracking Room . Convoys reroute
7:28around them – an effective tactic. But Ultra intelligence is slow, and sometimes it takes up to
7:3472 hours to de-crypt German communications. There are also periodic blackouts when Germans alter
7:40their settings – including almost all of 1942. And, as the number of U-boats at sea increases,
7:46the likelihood of evading them decreases. Ultra is vital as a wider strategic tool but cannot
7:52pinpoint U-boats preparing to attack. That’s where other technology comes in.
7:57By early 1943, more allied escorts are equipped with better sonar and radar equipment. Underwater
8:03ASDIC sonar can listen for submerged U-boats, gauging range and bearing. Not only does this
8:09reveal approaching U-boats, but allows for more accurate use of anti-submarine weapons,
8:14like the Hedgehog and depth charges. Meanwhile, ships and aircraft equipped with
8:18the new 10-centimetre radar can detect U-boats on the surface. None of these tools are perfect,
8:24but when combined with others, they create a near impenetrable network of defences:
8:31“The first indication of a U-boat attack would be from the ASDIC people who would pick up a
8:35contact... you could hear these pings... and the difference between the ping and the pong is the
8:40distance how far the submarine is away. When they think they’re right over the top of the submarine,
8:45the order is ‘Fire’. That means the depth-charges go... A colossal volume of water would come up...
8:51it was almost like lightning going across the water. In daytime it’s a
8:55fantastic thing to see.” (Bailey 67/68) German submariner Anton Staller aboard
9:00U-188 is on the receiving end of a depth charge attack in March 1943:
9:07“Alarm bells shrilled loudly... “Destroyer on the starboard bow... Range about 5,000
9:12meters!”... A quick glance at the manometer showed me that we were at 100 meters,
9:17at the same instant for the first time I heard ahead of us the roar of exploding depth charges.
9:23Now I discovered how appalling loud these sounded under water. Though fearful I concentrated on my
9:29hydrophone wondering if I would ever hear anything again in my life... ” (Willman 49)
9:38Another important Allied development is High Frequency/Direction Finding, known as HF/DF or
9:44“Huff Duff”. This can detect German U-boat radio communications out to 25 kilometres,
9:49close enough to pursue and attack. It greatly outranges surface radar and helps allow escorts
9:55to be more proactive. The technology existed since 1942, but in 1943 it’s much more available,
10:02with at least 2 HF/DF equipped ships per convoy. With this comes more powerful anti-submarine
10:07weapons and better organisation. Previously 6 escorts were considered adequate to protect 24
10:14merchantmen, but civilian experts led by Professor P. M. S. Blackett, find that eight escorts can
10:19protect 48 merchant ships just as effectively. This combines smaller convoys into larger ones and
10:26frees up escorts which can become mobile support groups assisting specific convoys under attack.
10:32And finally, there are more Very Long-Range bombers and escort carriers. By May,
10:37Coastal Command has 49 VLR bombers, up from 17 in February. Although dwarfed
10:43by the hundreds of bombers attacking German industry, this number is enough to close the
10:47air gap. Aircraft like B-24 Liberators, Whitley bombers and Sunderland and Catalina Flying boats,
10:54become vital submarine killers, quickly accounting for around half of U-boat losses.
11:00The combination of new tools and tactics is devasting to the U-boat fleet. In April,
11:05the battle balances out, as the Allies lose 39 merchantmen but sink 15 U-boats.
11:11May 1943 is the decisive month, especially the voyage of convoy SC-130. Heading to Liverpool
11:18from Halifax, Nova Scotia, the convoy has 37 merchantmen and 8 escorts, several equipped
11:24with High Frequency Direction Finding and new 10-cm radar. German naval intelligence identifies
11:29the convoy and gathers up to 25 U-boats in three wolfpacks to attack to attack. Donau 1 and 2
11:36approach from the south-east, while Wolfpack Iller is already in the area. The plan is to
11:41attack the convoy in the airgap, but British Ultra intelligence is aware of this. However,
11:46a system failure means the information is not passed to the escort commander. Even so, when
11:51the attack opens on May 18, the escorts proactive sweep for the U-boats and spoil their attacks,
11:57while the convoy also makes evasive turns. Soon the battle moves within the range of approaching
12:02Allied aircraft which hound the U-Boats and force them to submerge. By May 21st,
12:07U-boat command abandons the attack. The Allies sink three U-boats and damage
12:12another with no losses. On board one of the sunken U-boats - U-954 – is Admiral Dönitz youngest son,
12:19Paul, who dies with the rest of his crew. The SC-130 battle is the pinnacle of a
12:25terrible month for the Kriegsmarine, in which they lose a total of 41 U-boats – almost 25% those
12:32operational . Kapitänleutnant Peter-Erich Cremer at U-Boat Staff Headquarters later recalled:
12:39“This May situation was quite out of hand: as I was soon to learn, the number of boats that failed
12:45to return from patrol reached... more than one a day, and there was talk of “Black May”.” (Gannon)
12:52On May 24, Dönitz orders his U-boats to withdraw from the Atlantic until better
12:57equipment and countermeasures are available. So why did things go so wrong, so fast for
13:02the U-boats? Allied developments are one factor, but there were also German weaknesses. Firstly,
13:08the Germans had poor intelligence on Allied capabilities, especially High Frequency Direction
13:12Finding, radar, and Enigma decryption. As a result, submariners didn’t know how to
13:17avoid or compensate for them. Secondly, Dönitz’s top-down approach required constant radio reports,
13:23especially before an attack . This gave British Ultra and HF/DF detection more chances of locating
13:29them. During the SC-130 battle, there were 104 HF/DF reports, allowing the Allies to pinpoint
13:36the U-boats. Thirdly, the Kriegsmarine lacked reliable air cover. Dönitz demanded more from
13:41Hermann Göring’s Luftwaffe, but Göring resisted diverting resources away from his own interests.
13:47The increase in U-boat numbers also didn’t mean a proportionate increase in sinkings,
13:51although the sheer number of active U-boats still worried the Allies:
13:56“By April 1943 the average kill per U-boat at sea had sunk to 2,000 tons. This might be interesting
14:03as a sort of sporting score, but the number of U-boats operating had so greatly increased that it
14:08was of little significance in solving the problem. When Daniel Boone, who shot fifty bears a year,
14:13was replaced by fifty hunters who averaged one each, the bears saw no occasion to celebrate the
14:18decline in human marksmanship.” (Van der Vat 316) But individual U-boat performance and crew
14:24experience, were dropping quickly. In 1940, U-boat commanders had on average
14:28two years' experience. In 1943 this was only 8 months. Most U-boat captains killed in May
14:351943 had only one or two patrols to their name. In 1940, 2% of U-boat captains were responsible
14:42for 30% of sinkings. All these so-called “aces” had entered the Kriegsmarine before 1935,
14:48but by 1943, the veterans of the early war were gone. Roughly 850 U-boats – about 75% of the total
14:56built and crewed during the war – would never damage an Allied merchantman. In November 1940,
15:02the average tonnage sunk per U-Boat per day was 430 tonnes. In January 1943, it was 65.
15:12From 1939 to early ‘43, the Atlantic is the only theatre in which Germany successfully
15:17maintained the offensive. But now even there, they are in retreat. Dönitz’s withdrawal is not
15:23meant to be permanent though. He fast-tracks new U-boat developments and shifts back to a smaller
15:29group tactics, but the U-boat wolfpacks never make a meaningful return. Instead,
15:34the Atlantic becomes the logistical highway for the Allied invasion of Europe.
15:39Two years after “Black May” for the German U-Boat fleet, Admiral Dönitz becomes Head of State and
15:44Supreme Commander of the Armed Forces of Nazi Germany. After, that is, Adolf Hitler and Joseph
15:49Goebbels commit suicide in the Reichschancellery bunker as the Red Army is closing in on the
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