llied response During WW 2The North Atlantic Run: The Submarine war and the Allied Response
In September 1939, with the beginning of World War II, German U-boat operations got under way against allied forces; the allies responded to the U-boat threat with a number of counter measures.
The combined affect of protection of ships by convoys, harassment of U-boats by airplanes, and other anti-submarine warfare measures, reduced the ability of the U-boats to cut Britain off from her
suppliers in North America. In order to assess the effectiveness of the allied response, it is first necessary to look at the U-boats. In looking at the U-boats it is not only necessary to look at the
various types of U-boats and their deployment, but also to look at the German’s goals and the tactics that they employed in an attempt to reach those goals.
The Treaty of Versailles ending world war one prohibited Germany from having any U-boats. When the treaty was changed under The Anglo-German Naval agreement, one of the things that the
Germans did to rebuild their navy was to rebuild the U-boat wing. Their first U-boats were for general sea-going and coastal abilities, the U-boats first built for this purpose were types I and II. The type I had a surface speed of 17.75 knots and 8.25 knots submerged on electric engines, for armament it had 4.1 inch
and 22 mm. anti-aircraft guns and six torpedoes. In comparison, the type II had speeds of 13 knots surfaced and 7 knots submerged with three torpedoes and one 20 mm. anti-aircraft gun. The type II was
The Germans developed other U-boats between types III and VII, but the most popular model came with the type VII. The type VII had a displacement of 500 tons and with about 700 built, became the German’s main U-boat. It was equipped with a 3.5-inch anti-aircraft gun, four bow torpedo tubes, a single stern torpedo tube, and carried 14 torpedoes; it had a surface speed of 16 knots. The Germans also built several other U-boat types, the most popular being the type IX with a displacement of 750 tons and 150 being constructed. The type IX had a 4.1-inch anti-aircraft gun, 4 bow torpedo tubes, 2 stern tubes, and carried 19 torpedoes; it had a surface speed of 17 knots. Along with these main U-boats the Germans also had 10 supply U-boats built for refueling their other U-boats to extend their range. The type XIV U-tanker had a displacement of 1688 tons and had no torpedo tubes, instead the room was used to carry 635 tons of fuel, which could be used to resupply about twelve other U-boats. All of these U-boats were, as
with the types I and II, slower under water as they had to switch to their electric engines, their speed was thus reduced to about 6 or 7 knots.
These U-boats used, or tried, several different tactics against the allies during World War II to meet their war aims, which was to attack “. . . Britain’s supply lines . . . for the achievement of our naval strategic aims . . . ” to cut her off from her suppliers in North America. Militarily, the Germans tried to use the U-boats in support of other operations. The most famous of these was the invasion of Norway in April 1940. The Germans had planned to use the U-boats to protect their landing vessels against British attack while troops were dropped of in Norway and the vessels returned to Germany. During the invasion the Germans used all the U-boats that were available, assigning them primarily defensive roles. Thirteen U- boats were used to prevent the British from interfering in the landings in Norway and another four U-boats were then used to protect German communications lines between Germany and Norway.
Another thirteen were used to attack the British Home Fleet if the British decided to send them to interfere with the invasion. The use of the U-boats in the invasion was basically a failure because
their torpedoes were adversely affected by the high latitude as well as the degaussing of the British vessels. The magnetic detonators therefore would not go off.
The primary use of the U-boat was against traffic between Britain and North America. In these operations the Germans had two basic tactics, operations on their own, and operations in what were
termed Wolf Packs. The U-boats had tried Wolf Pack tactics as early as 1937 in training exercises, but with the outbreak of the war wolf packs were deemed unfeasible due to the inability to coordinate their actions; the U-boats were left to operate of their own, wandering the seas looking for targets to fire upon. Thus they did not sink as many enemy ships as would have been liked. The head of the German U-Boat, Admiral Dnitz, developed Wolf Pack tactics. He developed this idea to counter the use of the convoy system that used escorts to protect the ships. He thought that you had to throw everything that you had, in a coordinated fashion, at the enemy in order to destroy him. Dnitz said in his memoirs that,
. . . It is essential, in an attack on any given
objective, to be able to deliver the attack in as great
strength as possible – in other words, by means of
tactical co-operation and tactical leadership, to bring
a number of U-boats to attack simultaneously the given
objective . . . A massed target like a convoy, should
be engaged by massed U-boats . . . .
It was not until 1940 that the Germans were ready to employ these tactics. The problem of coordinating the attacks was fixed by the use of radio and aircraft patrols, to let the U-boats know
where a convoy was. When U-boat command would find the position of a convoy they would radio the U-boats its location and order them to proceed towards it in a line. The first U-boat to come in contact with the convoy would radio the others its precise location and the other U-boats would then meet up with the first U-boat and attack. The Wolf Pack tactics were extremely successful with 274 ships sunk in five months; one convoy in October, SC7, lost 20 of 34 ships to the Wolf Pack tactics, a loss of 59%.
An interesting variation of this tactic was also tired with limited success. It involved luring an enemy ship into a line of submerged U-boats and when it came into range they would fire upon it. An example of this was when the Bismarck and a line of U-boats near Greenland tried to lure some enemy vessels into their path, the plan failed when the Bismarck had to return to France. Another
attempt was made with U-boats returning home, the King George V passed near one of them but was left unharmed as the U-boat had no torpedoes!
With these tactics in place, the allies met a formidable adversary. To deal with the U-boats the allies implemented several countermeasures, the most famous and effective of these measures was the convoy system and the use of aircraft to attack, destroy, or scare off the U-boat.
At the outbreak of the war, Dnitz’s allied counterpart was the First Lord of the Admiralty Winston S. Churchill, the future Prime Minister. In September of 1939, Churchill used several measures against the U-boat threat. Firstly, he employed the intelligence apparatus of Britain against it to analyze the U-boat threat. On September 5th, 1939, he wrote to Admiral Pound and others,
. . . What does Intelligence say about possible
succoring of U-boats by Irish malcontents in west of
Ireland inlets? If they throw bombs in London, why should
they not supply petrol to U-boats? Extreme vigilance
should be practiced, and the closest contact maintained
between the DNI Director Naval Intelligence and ‘C.’
By 1941 Naval Intelligence even began to break the German codes used to encrypt communications with their U-boats; they also used radio direction finders to pin-point the location of the U-boats. This allowed the British to be able to divert convoys from where they knew U-boats to be.
Along with the increased vigilance of, and cooperation between, the intelligence services against the U-boat threat, Churchill also recommended several other options to Neville Chamberlain. In a meeting with the war cabinet in September 1939, he said that “. . . All possible steps were being taken to
introduce the convoy system . . .” and that aircraft should be used to protect shipping “. . . on the South-Western approaches and off the coast of Spain.” Between the 8th and the 11th of September, he recommended that radar be installed on ships to help protect them against U-boat attacks on the surface and to help telling the difference between friend and foe. He also recommended to Chamberlain that a Ministry of Shipping be established to, among other things,
. . . provide and organize the very large ship-building
program necessary as a safeguard against the heavy
losses of tonnage we may expect from a U-boats attack
apprehended in the summer of 1940 . . . .
The biggest measure that the British used against the U-boat was one that they had learned in World War I, this was the use of the convoy system. In this system ships would all meet in a
common port, like Halifax or New York, and wait to be grouped together for a trip across the Atlantic ocean. The merchant ships would be grouped together in the center of the convoy, while their
escort ships, armed naval vessels, would surround them on the perimeter. The idea behind the escort system was to prevent a U- boat from getting in torpedo range of the merchant ships. The
problem with the escort system was that even though the ships were somewhat protected against attack, the act of getting into and out of a convoy slowed down shipping. The ships all had to meet in a
common port, cross the Atlantic at the same speed when some of the ships could have gone faster, and then break out of convoy formation in a common port on the other side of the Atlantic which
may not be the port that they had intended to go to. This slow down caused the amount of cargo to be ship by Britain’s merchant ship to be cut by one third. Even without attacking the convoys, the
Germans had succeeded in at least choking Britain’s supply lines some what.
Unfortunately, the convoys were susceptible to attack by concentrations of U-boats in the Wolf Pack tactics previously explored; the British needed other means to protect their shipping from attack by U-boats. They found part of the solution in the use of aircraft. The biggest enemy of the U-boat, was itself. Because it had to run on battery power when submerged, it had to surface when those batteries died so it could go over on diesel power and recharge them. Because it was on the surface, it was vulnerable to
attack. It was this problem with the U-boat that the allies exploited.
To attack U-boats on the surface, the British employed aircraft. At first the aircraft had limited success against the U- boat due to problems in the bomb that they were using and in finding the U-boat and closing for the final attack. The bomb that they were first using was a 100 pound bomb. On the 5th of September 1939, an Anson of No. 233 Squadron tried to bomb a U-boat as it was submerging. The bomb that they dropped probably would have got the U-boat but for the fact that it skipped off the water like a rock that you would throw across a pond. The bomb bounced off the water and exploded in the air under the Anson. The plane was badly damaged and the crew had to put down in the ocean, luckily their
dinghy had not been damaged and they managed to survive. To fix the problem with the bomb skipping off the ocean if it did not directly hit a U-boat on the surface, the British modified a depth charge. The navy had been using a 450 pound depth charge against the U-boats, so the British took the Mark VII naval depth charge and modified it with “. . . a rounded fairing fitted to the nose and fins at the rear to stabilize it during its passage through the air.” The weapon had two disadvantages, in order to destroy a U-boat if it made a direct hit, the depth charge would have to roll off the U-boat and underneath and explode. Another
disadvantage was that the weapon had to be released lower than 100 feet in the air and the aircraft had to be flying slower that 115 mph or the depth charge would be damage upon impact with the water.
The aircraft also had problems in finding its target and methods. The aircraft were later equipped with radar, but when the aircraft got within five miles, sea clutter obscured the target from detection. The solution to this problem was the installation of a spotlight on the airplane, called the Leigh Light. The
aircraft would find its target using the radar and close on it, when it got almost within the range where it would lose the target due to sea clutter, it would illuminate it with the Leigh Light and make its final approach and fire upon it.
To deal with the threat from the air, the Germans began to install Schnorchels on their U-boats. The Schnorchel was a device raised to the surface of the sea that allowed the U-boats to vent their diesel engines thus enabling them to be used underwater, eliminating the need to surface to recharge the batteries. By 1943 all the U-boats were refitted with the Schnorchel and new U-boats had it incorporated in their design.
For submerged U-boats, there were two related methods for detecting them. The first was a crude form of sonar called ASDIC, named after the Allied Submarine Detection Investigation Committee that developed it. The ASDIC transmitted a sound that was reflected off any submerged object and then picked up by a directional receiver that would display the object on a range screen and you could read the direction of the object from a compass receiver. Once the range and direction was found, aircraft or escort vessels could be dispatched to go after the U- boat with the depth charges.
The second method of detection of the U-boat was the use of sonobuoys which operated in a similar fashion to the ASDIC/Sonar, except for the transmitters would be in the water and the plane
above would receive the signal. An aircraft would be dispatched to an area thought to contain the U-boat and drop one sonobuoy to get an initial reading. Four other buoys would be dropped along with the flight path of the aircraft, which was roughly a cloverleaf pattern. The last buoy dropped would then give the aircraft the precise position of the U-boat and the plane would go in for the attack with depth charges.
In a defensive approach, the allies also fortified major bases and sources of natural resources. An example of this is from the famous attack at Bell Island, Newfoundland, in 1942. In 1940, the
Canadian government sent two guns and two searchlights to the island which was a major supplier of iron ore for the allies. Two 4.7 inch guns were mounted at the ferry docks near a cliff, one of the searchlights was installed at the beach at the east end of the island and the other at the wharf of the ferry to the mainland. Unfortunately, these defenses were not enough and on September 5th, 1942, a German U-boat came into the harbor firing at three ships and sinking the Saganaga and the Lord Strathcona. The U-boat was damaged when it ran into the Lord Strathcona in the shallow waters, damaging its conning tower, that and the fact that she was being fired upon by another ship, the Evelyn B, forced the U-boat to
In looking at the efficiency of the allied response, it is best to look at the numbers of U-boats destroyed and by what method. Of 1,170 U-boats that were built, and 863 as operational U- boats, 784 of them were destroyed by the allies. Of the 784 destroyed, 34.5% were destroyed by surface vessels, 2.8% by allied submarines, 1.1% by mines laid by ships, 40.1% by aircraft on patrol, 7.9% were bombed in ports, 2.0% were destroyed by mines laid by aircraft, while 11.5% were lost to unknown causes. It is
clear that the allies had the most success at destroying U-boats from the air with a total of 50% of destroyed U-boat being lost to various methods employed by aircraft, whereas only 38.4% were lost
to methods employed by various naval vessels. Although no one response to the U-boat threat caused their defeat, the combination of all the methods that the allies used to attack the U-boats, and
protect against attack by them, helped lead to the defeat of the U- boat wing of the Nazi regime.
Dnitz, Admiral. Memoirs: Ten Years and Twenty Days. London:
Weidenfeld and Nicolson, 1959.
Gilbert, Martin. The Churchill War Papers: Volume 1, At the
Admiralty September 1939 – May 1940. New York and London:
W.W. Norton and Company, 1993.
Hezlet, Vice Admiral Sir Arthur. The Submarine and Sea Power.
London: Peter Davies, 1967.
Lautenschlger, Karl. “The Submarine in Naval Warfare, 1901-
2001″ Naval Strategy and National Security: An International
Security Reader. Edited by Steven E. Miller and Stephen van
Evera. Princeton, New Jersey: Princeton University Press,
Neary, Steve. The Enemy on Our Doorstep: The German Attacks at
Bell Island, Newfoundland, 1942. St. John’s: Jesperson Press
Price, Alfred. Aircraft versus Submarine: The Evolution of the
Anti-Submarine aircraft. London: William Kimber and Company,
Waters, Captain John M., Jr. Bloody Winter. Princeton, New Jersey:
D. Van Nostrand Company, Inc., 1967.