Research Paper
The U-Boat Campaign
Written by:
Chad Schaeffer
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The “Unterseeboot” or as it is more affectionately known, the U-Boat, was the
submarine employed by Germany successfully throughout both World War I and World War II.
This vessel could engage enemy naval warships but was more prominently noted for its
devastating effects as a commerce raider. Technology development both helped and hindered
the abilities of this craft, as the tools of war became more and more sophisticated. Looking at
the various technological advances that helped the war against the Allies and improved the
usefulness of the U-Boat will provide a clearer picture of why there were so many “unique”
classifications of U-Boats produced through-out this time period. U-Boats played a pivotal role
throughout World War I and also early points of World War II until strategies were developed
to counter them. This paper examines the roles they played, how technology helped and
hindered them, their successes, and also what ultimately led to their failure. Delving into these
topics should reveal why the U-Boat was such a pivotal asset early in the war, and what failures
the program suffered.
History of the U-Boat
World War I ended with the Allies discovering a few favorable tactics to use against the
U-Boats. The British Royal Navy had tried sending out Surface Hunters, thousands of ships that
were sent out to offensively scout out and scour the seas and oceans of U-Boats. Depth charges
became the weapon of choice for dealing with submerged submarines and were employed
heavily by the ASW (Anti-Submarine Warfare) ships. The Royal Navy also employed seaplanes,
non-rigid airships (also known as “blimps”) to scout out the seas for enemy naval forces. These
forces were largely ineffective in actually managing to kill Germany U-Boats, and even by 1915
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the kill rate by aircraft would remain for all purposes zero. 1 Mines would serve the purposes of
deterrence and lengthen voyages for U-Boats on patrol. They were reasonable for a large
number of submarine kills. The British submarines also played a part in torpedoing a large
number of U-Boats. The most important lesson would be the tactic of Convoying.
Convoying was initially opposed by the Royal Navy, while they were originally opposed
to idea based on it being a sharp diversion of naval resources and countering the normal tactics
of naval warfare. The Admiralty was fearful of whether or not merchant vessels were capable
following orders, given their non-military nature. Also there was the fact that the vessel of
slowest speed would dictate the overall speed for the entire convoy. Another fear was that
grouping such a large cluster of ships made them a prime target for the U-Boat skippers, one
that was too valuable to avoid. This tactic employed the use of destroyers, frigates, sloops, and
other craft to escort British merchant ships, which it should be noted, was not a new idea by
any means. After an initial test convoy, it soon became the standard for shipping in 1917, with
only ten ships lost out of some 1,500 merchant ships that reached the British Isles. In contrast,
one out of ten ships was lost when sailing independently. 2
Across the Atlantic, the US was becoming well aware of these successes. These offensive
tactics became so successful that in 1918 Assistant-Secretary of the Navy Franklin Roosevelt
would announce in the New York Times that they were “Defeating the U-Boat.” He also went on
to say that “Going after them and not waiting for them to come after us is the answer.” This
same article, would also note that maritime insurance rates were adjusted accordingly during
this period due to the successes that were occurring. 3
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News of the successes that Germany was experiencing with the U-Boats early into the
war, quickly reached the United States. These clips would bring back memories of the horror
stories of merchantmen from the First World War. The New York Times published an article on
October 15th, 1939 with the tagline “U-BOAT SINKS BRITISH BATTLESHIP; 396 OF 1,200 ON
ROYAL OAK RESCUED” which was a ploy to heighten the fear in the United States leading up to
the nation entering the war. Americans were all too well aware of how deadly the U-Boat could
be from their activities during World War I. Karl Doenitz would play a large role in this after his
reconversion. He initially favored the “Kriegsmarine” which was the build-up of big-ship surface
navy. But alas, he wrote in his memoirs “body and soul I was once more a submariner.” These
points would lead him to the conviction that “war with Great Britain was inevitable.” 4
Doenitz was well aware of the hazards and difficulties that would be faced by the UBoats in this war. He was convinced that Germany’s naval future did not lay with big surface
warships, but with the submarines:
This conviction derived from a close study of Germany U-boat records, official and
unofficial naval histories of World War I, and his own U-boat experiences. In his view,
the small, primitive Imperial Navy U-boat force had come very close to imposing a warwinning blockade against Great Britain. Had Germany build large numbers of U-boats
rather than big sgips for the High Seas Fleet, and had the Kaiser authorized unrestricted
U-boat warfare in the first year of the war, Doenitz concluded, Germany could have
achieved an early and decisive naval victory over the Allies. With proper organization
and planning and modern submarines and news tactics, he believed victory could be
realized in the war he saw coming.5 (Blair, Hitler’s U-Boat War)
To say the least, Doenitz played a pivotal part in establishing and devising the U-Boat
campaign/strategy that Germany would employ in World War II. He would ask for help from
the Luftwaffe early in the war in using aerial reconnaissance to assist in the deployments of the
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U-boats. The historian Clay Blair wrote: “Doenitz postulated, a force commander could in
theory shift the available U-boats by radio to positions to intercept the convoy” that were
discovered by this reconnaissance “for massed or group attack.” 6
Operation Drumbeat was part of Germany’s plan after the US entered World War II
following the events of Pearl Harbor, and simultaneous other Japanese attacks in the pacific. By
January of 1942, operations had begun in the coastal waters of Florida, targeting Aruban oil
supplies. Five large U-Boats were part of this initial strike; the long-range vessels were U-125, U124, U-66, U-130, and U-109. U-128 was also supposed to be part of this fleet but required
extensive repair which kept it from sailing with the others. This was a problem for Doenitz, who
had originally planned to sail twelve vessels, but was only allowed to use six vessels for the
operation, half of his original requested 12, into the US waters for the operation. This first strike
was responsible for the sinking of 25 ships and a total of 150,000 tons, of which U-123, sank
nine of these ships, and 53,000 tons. 7
The American operations did continue, as more U-Boats were deployed from their
French bases. These boats would be supported by support U-Boats, which functioned as refuel
and resupply vessels as early as May 1942, when U-459 began refueling some 15 U-Boats of the
northwest coast of Bermuda. This extended the patrol time of the fighting boats by four to
eight weeks time.
U-507 was the first boat to sink a ship in the Gulf of Mexico, sinking the freighter
Norlindo off of Key West. This vessel was sunk on May 4, 1942, and from that point forward
nearly one ship a day was lost in the Gulf of Mexico to the U-Boats operating in the waters.
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September 4th of that year would mark the final ship being sunk in these waters. The US Navy
finally took advice from the British Royal Navy and began to operate convoys along the eastern
coast in the middle of May 1942. This would cause Doenitz to withdraw his U-Boats and refocus
his attention on the North Atlantic. 8
Wolf Packs
The “Rudeltaktik” is what the Germans knew the Wolf Packs as, which were created by
Karl Doenitz. The Wolf Pack was a tactic developed to combat the Allies use of the convoy
system that was initially developed in World War I. The premise of this tactic is fairly simple; a
number of U-Boats would operate within a given patrol area. When a boat made a sighting of
vessels it would report this location and “shadow” the vessels it discovered. The German
commanders in charge of the U-Boats would then use this information to coordinate an attack
against the vessels, bringing the other U-Boats into play. Two-hundred and fifty wolf-packs
would be formed during the course of the conflict, all experiencing various levels of success
during the course of the war. 9
The death blow to this tactic came fairly early though. In 1941, U-110 was captured by
the British, providing them with an enigma cipher machine. This provided them with the ULTRA
messages that tipped them off to this tactic and known patrol lanes. Regardless, this tactic met
some success early on. Gannon writes: “In 1942 the convoy operations in the North Atlantic
were paused for U-boat patrols off the US east coast and the Caribbean, while the wolfpack
operations in the Arctic Sea against the convoys on the Murmansk run just began and
continued to almost the last day of the war. In Mid 1942 the wolfpack operations in the Atlantic
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started again and became increasingly successful culminating in the biggest convoy battles in
March 1943. However, the operations against convoys had to be stopped by the BdU after
heavy casualties in May 1943.” 10
The period of time between 1942 and 1943 brought some of the most pivotal series of
events that would ultimately lead to the failure of the U-Boat campaigns in the Atlantic, and
Gulf of Mexico. Wolf Pack strategy was forced to change abruptly by Doenitz on multiple
occasions. Wolf packs were ordered to change from night-time raiding too day-time raids, and
also ordering the U-Boats to fight against aircraft on the surface. 11 The increasing pressure by
the Royal Navy and the Royal Air Force (RAF) further forced Doentiz to pull the forces deployed
away from convoy battles. This also forced his hand in developing a new operational strategy,
one of silence and stealth. He also began to heavily pressure Germany industry to develop
countermeasures to Allied weapons. 12 During this period some 81 U-Boats would patrolling the
Atlantic Ocean shipping lanes, with the support of six refuellers.
The radio chatter these Wolf Packs required to operate effectively seemed to be a large
part of their undoing later into the war. To be “Lone Wolf” seemed to become a much more
reliable and effective means of waging war on the Allied merchant vessels. The U-Boat “Ace”
Werner Henke’s successes post 1942 provide quite a bit of evidence that long-range U-Boats
could be employed to much effect provided by the whether or not the captain and crew were
competent.
Technology
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A large part of the reason that Doenitz believed in the U-boat was due to technological
advances that German engineers made, and also took from various other specialists. These
advances consisted of more refined submarine construction techniques, more advanced
torpedoes, and more advanced communication systems.13 The U-Boats that were being
prototyped were far superior. They employed the usage of newer steel alloys, which were
stronger already. But they would also reinforce this new steel alloy by welding it together, for
stronger seams. This was opposed to using the more antiquated method of riveting the steel
together. This in affect would allow the vessels to overall be tougher, have more
maneuverability, and also allow for greater diving depths.14
The torpedoes that were being produced were also far superior. Larger warheads,
nearly twice the size of World War I models impressed Doenitz. Germany had also perfected
electric torpedoes, which lacked the wake which pointed directly back to the submarine that
had launched it. Also, magnetic fuses were being equipped to the torpedoes, allowing for
explosions beneath the keels of ships rather than hitting the more heavily armored sides of the
vessels.
There was quite a variety of U-Boats developed for the war effort or used throughout
the campaign. Initially relatively unchanged WWI boats were used, but in final days more
advanced boats such as the electroboats would be employed. Some of the most notable include
the Type IXB, which were long-range U-Boats that were used in US waters and off the coast of
Africa to much success. The Atlantic fleet consisted of VIIA, VIIB, VIIC (noted as the work horse
of the Atlantic fleet), and the revisions of the V11C /41 and /42. Also mine layers, and resupply
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boats were developed. The XB were the dedicated mine layers, and the “milk-cow” Type XIV.
Ten XIV U—Boats were commissioned to provide support to the attack boats and were used as
mobile refueling stations.
Revisions came in many forms for the U-Boat during its lifecycle. Stronger pressure hulls
were designed, as well as more advanced and powerful engines. One specific revision, the Mark
VIIC/42, this submarine featured a stronger pressure hull and more powerful engines. This
would allow the Mark VIIC/42 to have an increased surface speed, 2 knots added, and also
increased its nautical range by 3,500 miles. The stronger pressure hull would also allow the ship
to dive deeper, up to 300 meters, to wait out depth charger attacks. 15
One of the most important advances came too late in the war to change the tide back
into the favor of Germany. This was the invention of the Elektro boats, or Electroboats which
were developed by engineers Schuerer and Broecking. They utilized the hull design that was
developed by Professor Hellmuth Walter, for use in the Walter U-boat. Stashing additional
batteries in the lower section of the hull, that in the Walter boats’ had used for Perhydrol
storage, increased the performance and greater underwater times could be achieved. Doenitz
was satisfied by the increased performance these boats would achieve, and development was
commenced.
In January of 1943, theoretical calculations had been concluded and preliminary design
would be wrapped up in June. Of note about this Type XXI design, it could reach 18 knots for
1.5 hours while submerged, or 12-14 knots for 10 hours or 5 knots for 60 hours. Other notable
improvements included faster torpedo reloading with hydrolic torpedo reloading systems,
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incorporation of radar, sonar, and the schnorchel. One limitation of the design was its inability
to be used in shallow water operations. To combat this, a smaller Electroboat was designed, the
Type XXIII. In total, 119 of the XXII variety and 61 of the XXIII class would be commissioned
before the end of the war.16
Deck guns came in two varieties aboard the U-Boats. The two varieties of guns were the
8.8 cm and 10.5 cm deck guns, which saw some use early in the conflict. The issues with their
use, or lack of use once faced with the threat of Allied air craft, became so great that to save
weight and storage room they would be removed from most U-Boats in 1943, and were
completely absent from newer U-Boats. 17 They were effective against some smaller craft
though, such as the case of YP-389. This ship was a Navy patrol boat that was sunk by the U-701
in a bitter surface battle where fire was exchanged between the two. The U-701 specifically
used its 88mm gun to cause significant damage to and eventually sink the YP-389. This boat was
only recently discovered on a diving expedition in 2009, and recounts of its survivors provided
the details of the battle and its eventual sinking. 18
Some U-Boats were additionally equipped with more anti-aircraft flak-cannons or 20mm
guns. The U-527 for instance, was equipped as such and used these guns in its defense.
Ultimately, additional flak-cannons proved ineffective in deterring enemy aircraft attacks, such
as the case in the sinking of U-527. 19
The schnorchel was a bit of technology that Germany discovered in 1940 when they
captured Dutch submarines equipped with them. At the time, they saw little use for them, as
silence and stealth were strategies that were not fully employed until later in the war. The
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schnorchel allowed for the diesels engines to be run while the boat was submerged. This
limited speed, and was quite loud, basically rendering the boat deaf.
Boats were beginning to be equipped with schnorchel in 1943 when U-58 was used to
test its usefulness. But by mid 1944, only half of all boats stationed in France had schnorchels
retro-fitted onto the boats. Not solved on these retrofitted boats was the issue with the slow
speed the boats would be forced to maintain, the accumulation of other waste materials
aboard the boat, and the possibility for ear damage when the schnorchel become clogged
forcing the diesels to suck air from within the ship itself. 20
Some boats were equipped specifically as Mine Layers or support vessels, to resupply
the fighting U-Boats. The Type XB, of which the U-118 was one, such ship. It was equipped with
extra provisions in the amount of 80 days worth of rations, and fuel to refuel other U-Boats. It
also served the dual purpose as a mine-layer, such as the mine-laying it conducted at the Point
of Gibraltar. Its sinking and capture of surviving crew provided the Allies with a great deal of
intelligence of other operating U-boats. It also provided details on the operations of the vessels
and the equipment they used. Notes about booby-trapping the mines they laid was also
provided. 21
Allied Response
Early in the conflict, Doenitz was faced with the issue of not being able to keep enough
U-Boats in the water around Great Britain. Also problems with torpedoes led to confidence
issues with his commanders. Losses were also notably heavy as 2 or 3 U-Boats were lost a
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month to the Royal Navy, but in contract the U-Boats would cause the loss of “an average of 26
merchant ships” or in other words “280,000 gross tons of shipping to all causes monthly and
built on the average of 90,000 tons to replace” the lost vessels. 22
It is generally accepted that the Allied forces were ill-prepared for the U-Boat campaign
that was initiated in World War II. The Allies begun the war employing no real innovations
coming from lessons learned in World War I. In fact, the U-Boats that were used so successfully
in the early part of the war were of the more obsolete breed. Also losses off the coast of the
United States early in 1942 are attributed by the US’s refusal to use advice given to them by the
Royal Navy.
The pivotal year 1943 would be the turning point in favor of the Allied Forces campaign
against the U-Boat. Germany was unable to match Allied construction efforts, with construction
of merchant ships not far out-reaching the number of ships that were sunk. Also, by mid 1943
for the first time of the war, U-Boats sunk exceeded the amount of tonnage in materials they
were costing the Allies by nearly 30,000 tons. In fact, from 1943 through 1945, six hundred and
thirty-one U-Boats would be lost in conflict, or captured. This is in contrast to only 162 being
lost in the first four years of the conflict. 23
To put this in perspective, Herbert A. Werner, who was the commander of U-953,
provides an introduction to Iron Coffins, in which he describes his experiences during the war.
Yet even these figures do not reveal the full extent of the U-Boat disaster. Since only
842 U-Boats saw battle duty, and since 781 of these were lost, 93 per cent of the
operational U-Boat force was wiped out. In concrete terms, the toll seems even more
shocking. Our tremendous U-boat Force on the Atlantic Front was reduced to a mere 68
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operational boats by the time that the Allies invaded France in June 1944, and only
three of these boats were still afloat at war’s end. One of the three survivors was U-953,
which I commanded as her last captain. 24
The final part of the war, the 1943-45 period was the most significant in many ways,
especially when Doenitz would be forced to concede that the prime mission of the U-Boats was
to tie down the maximum number of enemy forces and supplies. This is a far cry away from
their original intended purpose of commerce raiding. 25 The reality was that even though the
fleet was now mostly newer boats, the German losses were still steadily increasing at a rate
which they could not keep up with. Germany had quickly lost its superiority in the sea, and
could not out sink American production.
Germany at first had the advantage of catching the Allies off their guard, ill-prepared
and not ready to counter the U-Boat. They forgot the importance of some of the many lessons
they had learned in World War I early into the conflict. So it really came as no surprise that
when tactics such as convoying and aerial and radio intelligence came back into vogue how
swiftly the tide would change. Getting the Americans to accept the concept of convoying was
difficult at first, but given the losses in the United States’ own waters, it was a lesson that
America quickly learned. But the intelligence that was gained from code books such as the
enigma machine and advanced radar and sonar technologies also played a significant part in
the defeat of the U-Boat.
Doenitz was confident early on in the superiority of submarine warfare to that of the
large warships that Kriegsmarine demanded. But was he short-sighted in this conviction? He
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was confident in the technological superiority that was given to submarines by advances in
their technology, but failed to consider fully that those same matured technologies would also
be prevalent in the counter measures that would be employed against them. In hindsight,
maybe more support could have been offered the U-Boats via carriers or air superiority also in
the shipping lanes. But the capture of the enigma device also greatly limited the effectiveness
of the U-Boat especially later into the war. That and the production capability of the United
States were able to out produce what the U-Boats could conceivably sink. The success of
Convoys in defending the merchant vessels ferrying over all the goods produced in America
would mean the end of the war ultimately for Germany, not simply for the U-Boat campaign.
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1
Clay Blair, Hitler’s U-Boat War, pages 3-49. Most importantly: “First notwithstanding huge loses of
merchant ships on their very doorstep, the Royal Navy continued to grossly underestimate the overall
effectiveness of the U-Boat campaign on British maritime assets…. Fourth, the admirals held, the
concentration of merchant ships into a single large body presented U-Boat skippers with richer targets,
which they were not likely to miss, even with poorly aimed or errant torpedoes.”
2
Clay Blair, Hitler’s U-Boat War, P15-17
3
The New York Times: May 22nd, 1918
4
New York Times Magazine and Hitler’s U-Boat War by Clay Blair
5
Clay Blair, Hitler’s U-Boat War, page 57
6
Clay Blair, Hitler’s U-Boat War, page 38
7
Information gathered from Operation Drumbeat written by Michael Gannon
8
Referenced from U-Boats Offshore by Hoyt, Edwin and Torpedoes in the Gulf by Melanie Wiggins, 1995.
9
Provided by Research at uboat.net
10
11
Slide Rules and Submarines/Meigs: “Doenitz changed the tactics of the wolfpacks from night-time to
daytime attacks and began ordering U-Boats to fight back from the surface when surprised by aircraft.”
12
Slides Rules and Submarines/Meigs: Page 127 “In May 1942, the Royal Navy and RAF’s Coastal
Command inflicted losses on U-Boats that forced Doenitz to pull his forces back from convoy battles.
Faced with unprecedented losses, he ordered his U-Boats to adopt a new operational strategy of silence
and stealth, while he pushed Germany industry to develop countermeasures to Allied Weapons, along
with a whole new generation of submarines.”
13
Clay Blair, Hitler’s U-Boat War, Page 37
14
Clay Blair, Hitler’s U-Boat War, Page 37
15
of Slide Rules and Submarines/Meigs: Page 127 Dealt with how Germany attempted to safe guard
their U-Boats in fright of advancing technology changes
16
Information primarily pulled from The Type XXI U-Boat: Anatomy of the Ship by Fritz Kohl.
17
Information provided by uboat.net
18
From Winston Salem Journal: U-boat Casualty Maritime archaeologists discover WWII Navy patroller
off Hatteras,
19
Provided by declassified US Navy document detailing the sinking of U-527 and intelligence gathered
from survivors of U-527.
20
The Dutch role in the development and deployment of the submarine Schnorchel.
The Journal of Military History 69, issue 4, pages 987-1012 (October 2005)
21
From notes about the sinking and interrogation of members of the crew of U-118.
22
Slides Rules and Submarines/Meigs: Page 20
23
Herbert Werner, Iron Coffins: Page325-326 Appendix data graphs and tables detailing the losses
endured by Allied and Axis forces.
24
Herbert Werner, Iron Coffins, P xvii
25
Timothy Mulliigan, Lone Wolf: Page 219Discussion and exposition upon the reality of the Henke and
how the U-Boat campaign had changed post 1942.
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Bibliography
Navy Department, Report on the Interrogation of Survivors of U-118:
http://www.uboatarchive.net/U-118.htm
Divisional of Naval Intelligence “Post Mortems on Enemy Submarines: U-527”, July
23, 1943, http://www.uboatarchive.net/U-527PostMortem.htm
“Defeating the U-Boat, Says F.D. Roosevelt” The New York Times, May 22, 1918
Blair, Clay. Hitler’s U-Boat War. Random House, 1996.
McCue, Brian. U-Boats in the Bay of Biscay: an essay in operations analysis. National
Defense University Press, 1990.
Mulligan, Timothy. Lone Wolf: The Life and Death of U-Boat Ace Werner Henke.
Praeger, 1993.
Werner, Herbert A. Iron Coffins; a personal account of the Germany U-Boat Battles
of World War II. Rinehart and Winston, 1969.
U-boat Casualty Maritime archaeologists discover WWII Navy patroller off Hatteras,
Winston Salem Journal, September 13th, 2009.