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Von Rom -> (7/26/2003 8:16:14 AM)
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Here is a paper I have re-produced in part that examines the U-boat impact on the Allied war effort. It was written by Michel Thomas Poirier, Commander, USN.
It is worth reading. And while reading it, consider the impact, if Germany had committed even more U-boats to the war effort.
Chief of Naval Operations
Submarine Warfare Division
RESULTS OF THE GERMAN AND AMERICAN
SUBMARINE CAMPAIGNS
OF WORLD WAR II
By
Michel Thomas Poirier
Commander, USN
20 Oct 1999
A Short Lesson on Naval Strategy
Traditionally, naval forces seek to gain victory by defeating opposing naval forces, thereby allowing unfettered use of the seas to project power to distant areas of the world. The American theorist Alfred Thayer Mahan most effectively articulated the view that destruction of the enemy battle fleet was the precursor to effective control of the sea.(9) The U.S., British and Japanese Navies all subscribed to the importance of Mahanian battle and therefore focused doctrinally on the destruction of the enemy battle fleet.(10) This predisposition to force on force planning remains in the U.S. Navy today.
Mahan downplayed the importance of the guerre de course, the concept of employing naval forces against an opposing merchant marine.(11) Navies too weak to directly attack opposing navies have employed the guerre de course as a way to deny use of the sea to their opponents with historically mixed results. However, war during the industrial age has increased the importance of sea lines of communications (SLOCs). Twentieth century armies based overseas require substantial maritime support in order to supply their immense logistical needs.(12) Destroying or reducing the flow of the ships meeting these logistical needs constitutes an important vulnerability to the ability to project power overseas. Furthermore, some nations (including Japan), lack important natural resources, and must import enormous amounts of raw materials for industrial use. Interdiction of these resources by conducting attacks against sea lines of communications provides another means of reducing an enemy's ability to support modern warfare
U.S. planning today assumes that we will be able to effectively defend our flow of follow on forces with little thought as to how this will be done. Logistical planning is simply a matter of ensuring that the proper supplies are loaded on the right ships. The lessons learned from the campaigns we will study indicate that the United States should plan for the potential efforts of an adversary to attack American sea lines of communication in order to inhibit our ability to project power.
The German U-boat Campaign in the Atlantic: 1939-1945
At the start of World War II, the German Navy was too small to directly challenge the English fleet for control of the sea. The only strategic possibility for the Germans was to attack allied commerce using their small submarine fleet. Throughout the war, the German Navy conducted a classic guerre de course, using aircraft, surface units and, above all, submarines to attempt to destroy allied commerce. Admiral Donitz's (head of the German submarine force) strategy employed his U-boats at the weakest point in enemy defenses where they could sink a maximum of tonnage.(13) Donitz's goal, therefore, was to cut England's supply of war materiel and, later, to prevent American productive and military capability from influencing the European theater.
In six years of pitched battles throughout the Atlantic, German U-boats, often employing wolfpack tactics and night surface attacks, attempted to destroy opposing convoys. Throughout the war, Allied scientific and technical developments, along with improvements in tactical doctrine, competed fiercely against German technical and doctrinal development. In the end, the vast allied productive capability, which assured plentiful escorts and merchant ships, and superior tactics, weapons and sensors resulted in Allied victory. After May 1943, although they attempted several additional challenges to allied supply lines, the Germans never could truly contest Allied control of the sea.
Direct Effects
During the war the Germans sank 5,150 allied ships displacing 21.57 million tons. Of this, the U-boats were responsible for 2828 ships of 14.69 million tons.(14) To place this in perspective, the Germans sank the equivalent of the entire British merchant fleet at the start of the war.(15) Additionally, submarines destroyed 187 warships, including 6 aircraft carriers and 2 battleships.(16) However, this tremendous destruction came at a heavy price: the Germans lost 785 submarines of 1,158 constructed.
These losses and the loss of valuable cargo are the direct effects of the Battle of the Atlantic. In the end, however, the U-boats did not prevent the U.S. from supplying England with military and industrial goods or food, nor from building up U.S. forces in England (Operation Bolero), nor from providing Russia with substantial material help. Thus, most historians see the Battle of the Atlantic as a German failure.
Indirect Effects
There were, however, substantial indirect and second order effects on the allied war effort. These effects resulted in significant allied logistical constraints. For example, the indirect effects of convoying severely reduced allied transportation capacity. The Allies calculated that a ship took 18-48% longer to sail in convoy.(17) Donitz estimated the loss of time at 33% on average.(18) The impact on Army logistics and U.S. strategy was significant. In response to the German campaign, the U.S. ordered much greater quantities of munitions and supplies that was actually needed, in order to "fill the pipeline," to replace cargoes lost at sea and as a hedge against the Germans cutting the Atlantic supply lanes.(19)
The result of this "loss of time" combined with significant losses (up until July 1943, Allied merchant ship losses exceeded production) had two effects on the Allied war effort. First, the Allies needed to produce and ship more war material than was actually required in theater. Secondly, the Allies possessed less logistical carrying capacity than desired. As a result of the lack of merchant shipping and material, the U.S. Army significantly reduced the size of their planned buildup to far more modest proportions (the original intention in 1942 was to build a large army of 16-17 million men).(20) Although speculative, it is probable that such a reduction meant that the combined U.S. and British Armies would have been incapable of defeating the Wehrmacht without the sizeable Red Army in the war.(21)
Effects on War Production
The U-boat attack on allied supply lines had a pronounced second order effect on allied production priorities. Throughout the war, the Allies had to prioritize between warship, merchant and amphibious production (as well as other uses for steel). In the fall of 1942, the Allies increased amphibious shipping to their highest production priority in a crash program to prepare for Roundup (the planned 1943 cross channel invasion).(22) Yet this buildup came at a difficult time when the Navy was 'straining' to replace the losses from Pearl Harbor, construct a battle fleet to win back dominance of the Pacific and build sufficient escorts and merchants to prevail against the potent German U-boat offensive."(23)
By the winter of 1942-43, the Allies cut back the landing craft program and increased escort production in order to counter renewed losses to German U-boats.(24) Hall concurs, noting that landing craft production was removed from FDR's "must" (highest priority for war production) program comprising rubber, high octane fuel, aircraft, escort vessels, and merchant shipping and pointing out that the change in priority was due to the need to increase escort production.(25) Landing craft production fell off from 105,000 tons in Feb 1943 to 51,000 tons in July 1943.(26)
The Allies' lack of landing craft would logistically constrain allied forces for the rest of the war. General George Marshall noted a "shortage which would plague us to the final day of the war in Europe-the shortage of assault craft, LSTs, LCIs and smaller vessels. This he described as the greatest by far of all the problems."(27) The British official review analyzed the situation in a similar way:
"In so far as the delays in launching the offensive could be attributed to an insufficient supply of landing craft, they were in the last resort due to the high strategic and industrial priority which the Allied leaders assigned to the defense of the shipping lanes."(28)
Operational Impact of German Submarine Offensive
To get full measure of the effects of the Battle of the Atlantic on Allied strategy, we must look at the combined effects of inadequate numbers of landing craft and inadequacy of logistical means due to heavy losses of merchant ships. Hall notes that:
"At most conferences of the heads of governments, the shipping experts of both countries met to consider the shipping aspects of any plan under consideration. Account was taken in such discussions both of ships already existing and the timetables for the completion of new ships. Such conferences dealt with a series of facts, or probabilities, some of which it was not too difficult to estimate- such as existing tonnage, rate of production, rate of sinkings. Thus at the Casablanca Conference, in January 1943, shipping- including landing craft and escort vessels- played a major role in the choice between offensives in France, Sicily, Burma and the Pacific."(29)
Heavy shipping losses and the resulting lack of logistical capacity played a prominent role in ruling out a 1943 invasion of France. Experts calculated only 8 U.S. divisions could be transported to Europe (11 without convoy restrictions) by the spring of 1943. Even if the invasion was delayed till September, U.S. forces would number only 12 divisions- which combined with 13 British divisions would be badly outnumbered by the 44 German divisions stationed in the West.(30)
With a cross channel invasion out of the question for 1943, the Allies embarked on a major effort in the Mediterranean - yet logistical constraints and landing craft limitations played a key and limiting role in the formulation of strategy throughout the southern theater. For example, concern over the line of communications played a deciding role in limiting the Allied attack on North Africa to the west of that continent rather than an early allied lodgment in Tunisia.(31) Additionally, at the Casablanca conference, logistical constraints and security of shipping was the key consideration in the selection of Sicily rather than Sardinia as the next target for Allied attack, and in the strong American opposition to more ambitious undertakings against Italy or in the eastern Mediterreanean.(32)
During the fall of 1943, allied victory in the Battle of the Atlantic resulted in another change of allied war production priorities. Allied leaders pared back escort production and again increased the priority of amphibious assault shipping.(33) The change came too late to prevent serious restrictions on Allied strategy and the feasibility of operations throughout 1944. Lack of assault and merchant shipping continued to plague Allied planners and resulted in heated discussions at the Cairo and Tehran conferences of late 1943 regarding what operations would be pursued. Lack of lift resulted in abandonment of operations in the Eastern Mediterranean.(34) Despite FDR's promise to Chiang Kai-shek, the Allies cancelled amphibious assaults planned against Japanese forces in Burma.(35) Lack of assault shipping and the desire to maintain an attack up the Italian peninsula towards Rome, resulted in the Allies postponing the Overlord invasion by more than one month.(36) Of greater import, the same lack of assault shipping resulted in postponement of the invasion of Southern France (Anvil). Originally designed to draw mobile German forces away from Normandy, Anvil as executed in August was "disconnected strategically" from Overlord and served little utility.(37)
Reduced Strategic Mobility and the British Import Crisis
Logistical constraints, attributable to the Battle of the Atlantic, resulted in two interesting "what-ifs" affecting the allied effort in Northern France. First, divisions sent into the Mediterranean Theater were "irrevocably bound there for lack of shipping to deploy them elsewhere."(38) While these Allied divisions tied down German troops in Italy, they were unavailable to exploit or reinforce Allied efforts in Northern France, a theater, by the way, which was much more suitable for offensive operations and logistical support. Secondly, had U-boat successes continued for several months longer in 1943 the Allies might have been incapable of a cross channel invasion in 1944. British imports fell to lower than sustainable levels early in 1943, resulting in a request for the U.S. to turn over a large amount of shipping to provide for British import needs. Despite warnings that the total American lift to England and the Mediterranean in 1943 could fall from 1.5 million to 800,000 men, FDR approved the transfer of transports. Only the sudden and unexpected defeat of the U-boats provided a respite for the Allies-and allowed the transports to England to buildup adequate forces for a Cross Channel invasion in 1944.(39)
The U-boat guerre de course clearly imposed logistical constraints on the Allies and limited their strategic freedom of action. Indeed, one can argue that the Battle of the Atlantic may have delayed the conclusion of the war.
The disproportionate costs and logistical constraints imposed on the Allies leads one to question the verdict of history that the campaign was a "failure" for Germany. While ultimately, German submariners did not win a decisive victory in the Atlantic, these iron warriors clearly gained time for the German war machine- an extraordinary feat considering that Germany started the war with just 57 submarines and eventually fought the world's two biggest navies combined. The German clearly waged an effective guerre de course.
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