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ONE of the first orders which the German Naval Staff received from the Fuehrer on the outbreak of World War II read: "The Naval High Command is to wage the war at sea in such a manner that incidents with the United States are avoided under all circumstances." In September 1939, however, Grand Admiral Raeder was of the opinion that the United States would enter the war sooner or later regardless of how German naval warfare was waged. It is to be assumed that Adolf Hitler held the same view. The objective, therefore, was to delay the entry of the United States into the war until Germany's military position was sufficiently secure. In World War I the German Army High Command believed that its military position was secure after the conquest of Rumania in the winter of 1916-1917, and that the time for unrestricted submarine warfare had therefore arrived. The High Command was wrong. In 1939, the German leaders resolved not to repeat the error in judgment.
In World War II the German Naval High Command accepted from the start the restrictions which were imposed for political reasons, and it worked with the Foreign Office without friction. As was its duty, it constantly sought to sharpen the effectiveness of the methods employed in submarine combat, but it always recognized the primary position of policy in the conduct of the war.
In 1936 the German Government had accepted the London submarine agreement of 1930. This agreement provided that a merchant ship could be sunk only after visit and search, and after adequate provision had been made for the safety of the crew. It was not deemed "adequate" if the crew were merely given the opportunity to put out in lifeboats on the high seas. These provisions were quoted almost word for word in the new German prize rules which were promulgated shortly before the outbreak of the Second World War, and U-boat commanders received orders to conform strictly to them. In agreement with accepted international law they were relieved of the requirement to visit and search in the cases of definitely recognized troop transports, of merchant ships escorted by warships or airplanes, and of merchant ships which participated in warlike actions or were used to transmit information.
A few hours after the outbreak of the Second World War a German U-boat sank the British passenger liner Athenia without warning in the North Atlantic with the loss of 120 lives. Since the Naval Staff had no report of the sinking from the U-boats then at sea, and could not believe that a U-boat captain would act in disregard of his orders, it denied the participation of a German submarine. On command of the Fuehrer the Naval Staff maintained this denial even when it turned out that U-30 had in fact sunk the Athenia. The captain believed at the time that the ship was an auxiliary cruiser--an error which had some substance in that the Athenia was encountered far off the peacetime British shipping route. The Naval Staff had no part in publishing the foolish hypothesis that the ship had been sunk by a bomb explosion which Mr. Churchill had arranged in order to inflame American feelings. This was a product of German propaganda; the Naval Staff could not even protest the publication of the story since it knew nothing of it.
The consequences of the Athenia case were very undesirable for German naval warfare, for it not only created the impression abroad that Germany was already waging unrestricted U-boat warfare in violation of the London submarine agreement, but also resulted in orders that, in order to avoid similar incidents, no attacks should be made on passenger steamers even when they were proceeding under escort. This special provision for passenger steamers went far beyond what was provided in the prize rules and lasted until the summer of 1940.
During the first weeks of war another restriction which went beyond the prize rules was imposed on the Naval High Command. The Fuehrer wished to make France open hostilities, and directed that no action be taken against French ships except in defense of an attack; he directed, moreover, that the prize rules were not to be invoked against French merchant ships, thus putting the French in a more favorable position than the neutrals. The prohibition of attack on French ships was lifted on September 24, 1939.
The strict observance of the prize rules, and of the London submarine agreement, could of course be based only on the premise that the merchant ships would obey international provisions laid down for them. But the British merchant ships had orders to report by radio the sighting of German U-boats. They were also directed to run without lights at night, and were armed; they had express orders to use their weapons offensively as well as defensively upon encountering a U-boat. In conformity with the rules of international law, the employment of British merchant ships in gathering information caused the German Naval Staff to issue the order of September 24, 1939, to use arms against all merchant ships which made use of their radio when stopped. The order also provided that U-boats should strive to rescue the crews. On October 2 all restrictions on the attack on darkened ships were removed, since darkened ships are indistinguishable from auxiliary warships at night. However, for the time being, the lifting of this restriction was limited to the waters around the United Kingdom and France.
The first case in which a merchant ship made use of her armament against a U-boat occurred on September 6, when U-38 was fired upon by the British steamer Manor. On September 26 the First Lord of the Admiralty announced the arming of British merchant ships to combat the U-boats. This announcement was followed on October 1 by the directive of the Admiralty to merchant shipping: "The British Admiralty announces that German submarines are pursuing new tactics. British vessels are called on to ram every German submarine."
The German answer was the order of the Fuehrer on October 4, by which the U-boats received full freedom to attack merchant ships which were definitely known to be armed, though all possible provisions were to be taken for the rescue of the crews. Since this order gave the U-boats no protection against merchant ships which carried concealed armament it was extended on October 17 to include all enemy merchant ships. This marked the end of the first phase of U-boat warfare. Passenger liners continued to hold a privileged position and, as before, could not be attacked even though they were armed or steamed in convoy. The International Court of Justice gave the following verdict in Nuremberg on October 1, 1946, concerning the propriety of the German U-boat war against enemy shipping:
"Shortly after the outbreak of war the British Admiralty, in accordance with its Handbook of Instructions of 1938 to the merchant navy, armed its merchant vessels, in many cases convoyed them with armed escort, gave orders to send position reports upon sighting submarines, thus integrating merchant vessels into the warning network of naval intelligence. On October 1, 1939, the British Admiralty announced that British merchant ships had been ordered to ram U-boats if possible.
"In the actual circumstances of this case, the Tribunal is not prepared to hold Doenitz guilty for his conduct of submarine warfare against British armed merchant ships."
The problem of treatment of neutrals in accordance with international law was more difficult. If the war against the British lines of communication was to show decisive results then commerce by neutral ships must also be interrupted. Besides the right to visit and search merchant ships, international law contained the so-called contraband provisions. "Contraband" comprised all those things which could be utilized directly or indirectly for military purposes or, more broadly, all materials which served to strengthen enemy war potential. A neutral ship which carried contraband could be brought into port; and if it could be established with certainty that more than half her cargo was contraband, she could be sunk on the spot (in accordance with Article 73 of the prize rules) if for naval reasons it was impossible to bring her into port. The U-boat endeavored to observe strictly the prize-rule provisions governing neutral merchant ships, but errors were made because the U-boat captains suspected that enemy ships were misusing neutral flags, and sometimes because the procedure of the neutrals was inept. Moreover, it soon became evident that in this age of the airplane it is a military impossibility to undertake the process of visit and search for which a submarine must be surfaced for a considerable length of time, particularly when near the enemy's coast. In consequence the U-boat war in the North Sea had to be discontinued as early as September 30, since at that time the prize rules were still in effect.
Therefore it became necessary to attempt to induce neutrals to forego the routing of shipping to British ports. At the beginning of the war the German U-boats had orders not to stop Italian, Spanish, Russian and Japanese ships, because the Foreign Office hoped to stop the transport of contraband from these friendly states by political means. On November 4, in conformity with the United States neutrality law, President Roosevelt forbade American shipping to enter the so-called war zones. Following this precedent the German Government on November 24 addressed a note to the other neutrals which warned them of the dangers which they might encounter in the waters around the British and French coasts. After the way had been thus prepared for an intensification of naval warfare there followed on January 6, 1940, the declaration of the first so-called "operation area"--Zone A in the waters northeast of Scotland, the Orkneys and the Shetlands--in which the U-boats would sink neutral as well as other ships without warning. Subsequently other zones were specified until on May 24, 1940, a ring had been closed around England. Therewith all ships coming within a strip 60 to 100 nautical miles wide around England and on the French coasts were subject to attack without warning. Even now passenger liners, the merchant ships of the neutrals previously mentioned as friendly to Germany, and, by reason of a special economic agreement with Denmark, the so-called Danish "Malteser" ships were exempted. The exemptions presented an almost insoluble problem for the U-boats since they still had to determine on short notice the nationality of merchant ships encountered in the area where the enemy defense was strongest.
On August 17, 1940, with the intensification of naval warfare against Britain after the downfall of France, all the waters around the British Isles were declared an operation area, and the extension of enemy aerial patrol in the coastal waters made it necessary to extend the previous zone westward. Within these designated boundaries even passenger liners were now attacked without warning; only the merchant ships of the Irish Free State were assured of free passage when they had been previously announced and particularly marked.
It is, I think, fair to conclude at this point that the German Naval Staff had carried on and gradually intensified the U-boat warfare with skill and with regard for international law. It is of interest to refer again to the verdict of the International Court of Justice in Nuremberg. According to the Court, the declaration of "operation areas," in which neutral merchant ships were sunk without warning, was a violation of the London submarine agreement. But the Court made the following statement, on which the verdict against Grand Admiral Doenitz was based: "In view of all the facts proved and in particular of an order of the British Admiralty announced on May 8, 1940, according to which all vessels should be sunk at night in the Skagerrak, and the answers to interrogatories by Admiral Nimitz stating that unrestricted submarine warfare was carried on in the Pacific Ocean by the United States from the first day that nation entered the war, the sentence of Doenitz is not assessed on the ground of his breaches of the international law of submarine warfare."
The attitude of the United States was of decisive importance for the conduct of the U-boat war. As we have noted, Adolf Hitler gave the Naval High Command strict orders on the outbreak of war to wage naval warfare so that all incidents with the United States would be avoided. This effort was very much facilitated by the American Neutrality Act which was passed in the last years before the war. On November 4, 1939, however, Congress reversed the neutrality law, substituting for the arms embargo a "cash and carry" clause. Even more significant for the German Naval High Command was the proclamation by the American President of "combat areas," which American citizens and American ships of every sort were forbidden to enter. The boundaries of the operational areas which the German Naval Staff had declared on August 17, 1940 in the waters around England corresponded essentially with the extent of the combat areas. This offered extraordinary relief for the German conduct of the war at sea.
In September 1940, however, came the transfer of 50 United States destroyers from the United States Government to the British Admiralty, and then a succession of measures to support the British conduct of the war. "Ways must be found," declared Secretary of State Hull, "to insure that aid for Great Britain reaches its destination in the shortest time and maximum capacity." In accordance with this concept, after the occupation of Iceland (July 7), the United States assumed a large part of the responsibility for the security of British convoys between United States ports and Iceland. In September the United States assumed the further responsibility for the convoys in the entire western half of the Atlantic to 26° W, and, in the northern part of the Atlantic, even beyond. German leaders could only conclude that the United States had tacitly passed from a state of neutrality to a state of undeclared war.
Still German naval forces were required to try to avoid incidents with American ships, and the German captains sometimes let a sure-kill pass rather than risk the danger of political entanglement with the United States. Nonetheless, the sinkings of the Greer, the Kearney and the Reuben James followed. On November 14 the United States Congress by a vote of 212 to 194 repealed the provisions of the neutrality law which forbade the arming of American merchant ships, the entering of combat areas and the use of enemy ports by American ships. Now the German Naval High Command had to make a fateful decision. Should the war on commerce be continued unchanged within the current operations areas, or should German naval warfare be restricted in the endeavor to avoid incidents with the United States? The former course would unavoidably bring the United States openly into the war; the latter would in practice mean abandoning the effort to cut Britain's supply lines. The German Naval Staff was spared the necessity of deciding by the Japanese attack on Pearl Harbor. On December 11 the German Government declared a state of war between the United States and Germany.
We can only speculate as to the reasons which motivated the German Government to take the initiative in declaring war. For Adolf Hitler the development of German-American relations was closely linked with the Japanese stand on the Three Power Pact. If war between the United States and Germany should result from German actions which could be construed as a provocation of the United States, then there was danger that the Japanese Government would not regard the Three Power Pact as binding. When on December 7, 1941, the curtain which had previously veiled the development of events in the Far East had dropped and the attack on Pearl Harbor had definitely committed the Japanese to war, the way was then open to the German Government. The reaction may have been so strong that all the animosity which had been built up within the German Government in the war years against the attitude of the United States suddenly found release, and all deliberations and restraints which might even now have admonished its leaders to caution were swept away.
On September 3, 1939, the German Navy had a total of 57 U-boats, of which 46--a very high percentage--were ready for immediate employment. Of these only 22--types I and IX (700 tons) and type VII (500 tons)--were suitable for use in the Atlantic; the remaining 24--type II (250 tons)--could be used only in the North Sea. Before the war the German Navy had undertaken only a moderate amount of U-boat construction, because until late in 1938 it had accepted the view of the political leaders that Great Britain was not to be regarded as a probable enemy. Moreover, due to the political relationship with Soviet Russia at that time, the Naval High Command was concerned primarily with the conduct of war in the Baltic Sea and concentrated on preparing a defense against the Russian submarine fleet. According to the German-British Naval Treaty of 1935, the German Navy could have had 72 U-boats in the fall of 1939, if it had chosen to accept a relationship of 45 percent with the British submarine fleet, and a total of 160 U-boats if it had utilized the 100 percent limit. The monthly increase which was to be expected as a result of new German construction averaged only two submarines.
Thus the number of available U-boats was completely inadequate for effective submarine warfare. According to experience, one-third of the U-boats which were available for action were always under overhaul at the base, one-third were enroute to, or returning from, the operation area and only one-third were available in the operation area. Immediately upon the outbreak of war, therefore, the Naval High Command undertook a large scale construction program, by which deliveries would be gradually stepped up to 30 per month.
Despite the inadequacy of numbers, however, the Naval High Command held great hope for the effectiveness of this arm. The U-boat and its weapons had been considerably improved since World War I. Progress had been made in rendering the submarine quieter in operation, thus facilitating an unobserved approach to the enemy; and the bubble which revealed the firing of a torpedo, and the track of bubbles which marked the passage of an air-driven torpedo, had been eliminated. The destructive effect of the torpedoes had been considerably increased, and a marked improvement in the intelligence service had made it possible for the High Command to concentrate a number of U-boats for purposes of attack even when the submarines were operating submerged, a development of great tactical importance against convoys.
Aside from improvements in performance which were hoped for as a result of the lessons of World War I, it was expected that the vast expansion of the German Air Force would contribute greatly to the effectiveness of U-boat warfare. A primary weakness of the submarine is its limited range of vision, due to the lowness of the lookout tower; the airplane, with its almost unlimited speed and perspective, can be of invaluable assistance in informing a submarine about the location of the enemy. In view of the small number of U-boats available at the start of the war, the German Naval Staff was aware that this arm alone could not cut the British overseas trade routes. Consequently, it sought from the beginning to bring to bear all weapons of war which could be employed against enemy shipping--that is to say, not only the Navy's U-boats, surface ships, auxiliary cruisers and mines--but also the weapons at the disposition of the Air Force.
The Naval Staff believed that such concentration would in the course of time show decisive results upon enemy commerce. It also expected that the shortage of U-boats would gradually be remedied by the accelerated construction program. The relative naval strengths of Germany and Great Britain, which forbade the Germans to give battle with surface fleets, permitted no other course. However, there were two uncertain factors in the reckoning of the Naval Staff, one of which affected German strength and the other the enemy's. Prior to the war the potentialities of air power as an instrument of sea power had hardly been probed. Moreover, the German Air Force had been developed to meet purely continental requirements; its suitability for naval tasks had been neglected. The Commander-in-Chief of the Air Force, Field Marshal Goering, granted the necessity of providing for the tasks of the air arm in naval warfare, but despite constant pressure on the part of the Navy this program always came off second best. The Field Marshal also wished to retain under his own command whatever forces or matériel he provided, though he had no knowledge of naval matters. Upon the outbreak of the war, the Naval High Command brought about the modifications that would adapt the Air Force armament to the tasks of naval warfare, and the problems of command were also solved. But these changes came late. It was the inadequacy of German air power which was fatal for the success of U-boat warfare.
The other uncertain factor in the calculations of the Naval Staff was the speed with which the enemy would be able to improve and expand its defensive weapons against U-boats and planes, and to replace the ship losses. In the given situation, time worked for the enemy, since the German war potential was largely required for the land campaigns. Consequently the decision in the war on commerce had to be achieved fairly quickly--within a period of about two years at least. The prospect of accomplishing this with the means available at the beginning of the war was small, particularly in view of the hostile attitude of President Roosevelt toward Nazi Germany. The Germans had to expect that before long the inexhaustible war potential of the United States would be thrown into the balance on the side of the Allies.
As it happened, the degree to which the monthly sinkings of merchant ships exceeded new construction increased up to April 1942, then diminished until the end of the year 1942. From then on new construction exceeded the sinkings. This was the turning point of the war on commerce, and by September 1943 the shipping tonnage at the disposal of the Allies was as large as it had been at the beginning of the war and was increasing rapidly. These few sentences tell the story of the German war on commerce.
The Foreign Merchant Shipping section of the German Naval Staff kept a running and detailed study of the balance which resulted from the monthly sinkings and new construction--the vital balance of the naval war. Most of the ships sunk could be listed by name, and when they could not be named the reports were subjected to considerable discount. The estimate of new construction was based in part on German intelligence reports and in part on information given out by the enemy Powers. In general it can now be said that the estimate of total sinkings overshot the actual figures by a good deal, that the achievement of the U-boats alone was slightly overestimated, and that figures for new construction were somewhat below the production achieved by the enemy.
According to the German reckoning the monthly sinkings in the war on commerce during the first six months was about 250,000 gross registered tons. During this period the number of U-boats was reduced from 57 to 50. Even though the monthly losses averaged only two-and-a-half boats, the additions to the submarine fleet from the prewar building program were insufficient to cover the losses. In March and April 1940 there was a sharp falling off of sinkings, since the U-boats and Air Force were employed in the Norwegian operation. This undertaking brought to light a serious deficiency of the U-boats, for in northern latitudes the torpedo could not be fired magnetically, presumably by reason of the proximity to the magnetic North Pole. (In magnetic firing the torpedo can be exploded under the bottom of the ship, the most vulnerable part of the hull.) Moreover, when percussion firing was resorted to, the depth control mechanism of the torpedoes turned out to be undependable and the torpedoes frequently underran the targets. In short, it was apparent that the U-boats had no effective torpedo arm! This crisis lasted for some time.
The occupation of Norway brought with it only minor naval advantage, but the capture of the French Atlantic coast which followed soon thereafter resulted in a very great improvement in the conditions of operation for the German Navy. Now the German bases looked out on the broad Atlantic. The length of the journey to the combat area was considerably reduced; the percentage of U-boats in that area increased. At the same time, however, the operation area west of the British Isles was pushed farther and farther westward, as the enemy defensive measures--in particular the activity of the British Air Force--increased in strength and range. And it was now that the deficiencies of the German air support began to be very seriously felt. As the area of operations became more extended it became more and more difficult to locate the convoys and to concentrate the U-boats, which were scouting over a larger area, when a convoy was found. The need for aid from the Air Force became more and more urgent, but as the distance of the combat area from the coast increased, the range of the available German planes proved more and more inadequate.
Nonetheless, the situation was becoming dangerous for Britain. From May 1940, a month of particularly heavy sinkings, to the beginning of 1941, the figures of sinkings were about double those of the winter of 1939-1940. The agreement with the United States whereby the British Admiralty received the 50 destroyers was timely aid. There had been no increase in the number of U-boats available for operation in 1940, and the low point in the number of operational U-boats came on February 1, 1941, when there were only 21 available for action. There were 55 in training. But from the beginning of 1942, the number of operational U-boats increased by an average of 20 per month, and as the losses remained relatively moderate, the number of U-boats in action increased sharply. All told, 1,105 U-boats were commissioned during the war.
The considerable increase in the number of operational U-boats is reflected in the increase in ship sinkings in 1941; the successes in the first half of this year were particularly great. The entry of the United States into the war that December resulted in a great extension of the opportunities for attack, and hence brought a large increase in sinkings; it took the United States a considerable time to organize the defense of the coastal waters. The year 1942 was the high point in the German war on commerce; during six months of this year the Foreign Merchant Shipping section of the Naval Staff calculated that the monthly sinkings averaged more than 1,000,000 tons. This estimate was somewhat exaggerated; nevertheless, the successes were extraordinary. According to an official British report the losses of 134 ships with 860,000 tons in November 1942 were the greatest of any month of the war for the Allies. However, American and British new construction was now going full blast and began to approach the curve of sinkings.
The range of the U-boats was considerable; they operated not only in the Caribbean Sea but also off Capetown and in the Indian Ocean. In order to increase the period of operations in these distant waters submarine supply ships were developed to provide fuel and ammunition. Despite the primitive living conditions, the endurance of the U-boat crews proved to be almost unlimited.
In the summer of 1942, the gradually increasing defense measures of the United States in the coastal waters of the western Atlantic had forced the U-boats to shift their main hunting grounds to the middle Atlantic, where there was a gap between the American air patrol in the west and the British in the east. As yet the Allies did not have enough aircraft carriers to bridge this gap. The so-called "wolf pack" tactics--the simultantous assault on one convoy of a large number of U-boats under one command--now proved its worth. Some convoys were almost completely destroyed. However, the defense against the U-boats was steadily growing as enemy air superiority asserted itself more and more; plainly it would not be long before this gap in the Atlantic was closed. The German Naval Staff seems not to have viewed the danger impending from the growth of enemy air strength with the necessary dispassionate judgment.
The growing number of corvettes, frigates and other defensive vessels also served to limit the attack of the U-boats. The vicinity of a convoy came more and more to resemble a zone in coastal waters in which surface passage of a U-boat was impossible. U-boats still advanced to their operation areas on the surface, however, and when they located a convoy tried to get as close to it as possible before submerging for the torpedo attack. Very logically, the defense sought ways and means to deprive the U-boat of the advantages of her surface speed. Radar solved this problem, and made it possible for planes to locate surfaced U-boats. As early as the end of 1942, radar-equipped planes scored their first successes, when U-boats arriving and departing from French coastal waters were subjected to surprise attacks from the air during night passage on the surface. The planes appeared so suddenly that the U-boats could not avoid them by diving.
The submarine appeared to be helpless in the face of this new method of attack, and from 1943 on German losses took on threatening proportions. To be sure, it did not take long to equip the U-boats with the first protective devices against this new danger, but this apparatus, intended to give the U-boat warning that enemy radar was searching for her, itself disclosed to the enemy aircraft the position of the U-boat--and at approximately double the distance at which the plane's radar could otherwise locate the submarine. Losses continued to mount; in May 1943 almost 40 U-boats were lost, as against an average increase by new construction of about 20 U-boats. Yet shortly before--March 1943--despite the ever-increasing difficulties of attack, sinkings of merchant ships had amounted to 900,000 tons.
In the course of 1943 all U-boats were equipped with efficient instruments which gave warning of enemy radar search without betraying their own position. Moreover, the anti-aircraft armament of the U-boats was increased, so that it was possible for them to fight off attacking planes. These measures afforded some relief, but the fact remained that the enemy air force, considerably increased in strength and using skillfully the new radar equipment, was enabled in time to establish a zone in which the U-boats could no longer operate on the surface. Even the charging of the batteries came to present a most difficult problem.
What conclusions did the German leaders draw from this new situation? First they made the only possible decision, i.e. to withdraw the U-boats from operations in the main danger area--the Atlantic--and to assign them to other areas which would probably be less fruitful but which were also less subject to pressure from the enemy air force. The German Air Force was too weak, and planes were too greatly needed on all fronts, for German air power to challenge successfully the enemy air superiority. However, this interruption of U-boat warfare in the Atlantic could be only a temporary expedient. Could decisive results again be expected from U-boat warfare? That was the fateful question that had to be answered. Only if this question could be answered in the affirmative was it reasonable to put into the forced program of U-boat construction the enormous quantities of scarce industrial material which it required. The building program required approximately 60 percent of the entire output of the German electrical industry, and a considerable part of the steel production. And beyond all this was the cost in lives of the U-boat campaign. Were these sacrifices justifiable?
Under the dominant influence of the Commander-in-Chief of the Navy, who was also the former Commander of U-boats, Grand Admiral Doenitz, the German High Command answered in the affirmative. The German leaders never abandoned hope that U-boat warfare could be revived and could exert decisive effect on the war. Various positive factors contributed to this attitude. A U-boat with a radically new drive had been developed, which would have a speed submerged of about 18 knots and a larger under-water range. This appeared to ameliorate the greatest tactical weakness of the U-boat--the slowness and danger of its trip to the operation area. The higher submerged speed of the new boats relative to the speed of a convoy would also, it was hoped, make possible new and more effective methods of attack and defense. It was hoped to have the new U-boats available for action by the summer or fall of 1944. Actually none got into action before the war ended.
The available U-boats were, however, being fitted with the so-called "snorkel," a trunk which supplied atmospheric air for the diesel motors and permitted the charging of batteries underwater. This greatly lessened the danger of air attack and permitted the U-boats to operate again in the coastal waters from which they had been driven by the enemy air force.
The first snorkel U-boats were employed in operations in the summer of 1944; they fulfilled all expectations. The boats returned from three weeks in areas with strong pursuit and radar defenses having scored from three to five sinkings. They did not surface a single time during the whole period. To be sure, these submerged cruises radically altered the fundamentals of U-boat warfare, for the possibilities of scouting from the U-boat were still further reduced; without air reconnaissance the U-boats became more or less blind, and the possibility of finding a convoy in the open sea was more or less a matter of chance. It was evident that worthwhile operating areas for the new U-boats would be found only near the harbor approaches.
Moreover, considerable improvement of the main weapon of the U-boat, the torpedo, was in process. This consisted of a supplemental device by which the propeller noises of a fast ship pulled the torpedo toward it. This weapon, designated by the code word Zaunkoenig, was available after September 1943 and was particularly effective against the escort destroyers. Even so the U-boats could seldom break up the strong enemy destroyer screen to get at the real object of the war on commerce, the merchant ships.
Another strong argument for the continuation of the U-boat war with all forces was the burden which it placed on the war potential of the enemy. The threat of U-boats required the formation of convoys, the building of patrol vessels and defensive weapons, the construction of merchant ships, and the maintenance of an air organization spanning the oceans--all of which tied down men and materials which might have been employed in other phases of the war. This was no doubt a factor of very great importance; but it had to be weighed against the drain on German war potential.
When Grand Admiral Doenitz represented to the Fuehrer with all the weight of his position and personality that the U-boat war should remain a primary aspect of the German war effort, he was no doubt influenced by the exaggerated expectations built up on the alleged lessons of U-boat warfare of World War I. But the illusion of the German leaders that successful U-boat warfare could be revived after the reverses of the spring of 1943 was smashed by the hard realities of the last two years of World War II. To be sure, the curve shows a slight increase of sinkings after the summer of 1944--a success which was due to technical improvements of the U-boat, anti-radar apparatus, snorkel and the Zaunkoenig torpedo. Thereafter, however, the monthly sinkings seldom exceeded 250,000 tons, as against an increase of enemy merchant shipping by new construction of over 1,000,000 tons per month. When the first new U-boat types on which such great hopes had been placed were ready for action, the war was over.
A sober and critical German estimate of the situation should have foreseen this result. The blow which the U-boat war suffered during 1943 was induced by the enemy use of radar, but it is not true that this device was responsible for the failure of U-boat warfare. The reasons lie deeper. The downward trend in U-boat warfare had set in at an earlier period--April 1942--when the gap between merchant ship sinkings and new construction began to decrease. The two major factors were the tremendous effort undertaken in the enemy shipyards to replace the lost tonnage, and the attainment by the enemy of air supremacy in the Atlantic. Both developments were apparent in the spring of 1943, and in the nature of things could not be altered by Germany. The American ship-building effort was beyond the reach of German war measures; and there was no question of wresting air supremacy from the enemy in the Atlantic when his air superiority had begun to be felt within the Reich itself.
Under these circumstances it is difficult to understand how the German leaders could reasonably have expected to inaugurate a decisive new era of U-boat warfare in the fall of 1944, even if the dangerous situation on other fronts and the effects of enemy bombing on German production were discounted. The production record of American shipyards was known in Germany; a lull in U-boat warfare lasting only until the beginning of the "new era" would result in an increase of Allied shipping of about 10,000,000 to 12,000,000 tons.
Naturally it would not have been wise to discontinue the U-boat war altogether, but there was a middle course. The submarine campaign could have been continued without the stepped-up new construction program, by conservation of U-boats in use. There were 435 U-boats in service on June 1, 1943, after deducting the high losses suffered in May--an appreciable figure compared with the 57 U-boats at the beginning of the war. Great quantities of valuable war matériel would thereby have become available for planes, tanks and anti-invasion preparations; and these U-boats would have prevented the enemy from slackening his defense measures. To be sure, such a decision would have been a clear admission that the U-boat had ceased to be a decisive factor in the war. The strength of character necessary for such an admission was not forthcoming from the responsible German leaders.
After the spring of 1943 deep tragedy overshadowed the heroic war service of the U-boat crews. Their courage and their readiness to sacrifice right to the end could not alter the fact that they were fighting a losing battle. Of about 1,160 German U-boats which were in service during the war, 630 were lost by enemy action up to the end of April 1945. In April there were available about 400 operational U-boats, including those used in training. During the first part of May, up to the conclusion of the armistice, 108 more U-boats were sunk, or which 89 were scuttled by their crews. Of 40,000 German naval personnel which manned the submarines, 30,000 were lost in action--in truth a frightful proportion. By far the greatest part of the losses were suffered in the period of decline, 1943-1945. Those who survived this catastrophe may note with proud satisfaction what an opponent has to say concerning them: "There is no reason to suppose that they would not have fought on in a losing campaign if the defeat of the German Army had not brought collapse and surrender. Their morale was unimpaired to the bitter end." Thus reads the official British record.