Kriegsmarine Part I

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Kriegsmarine U-boats between 1935 and 01 September 1939 (Part 1)

Enormous domestic and foreign literature has been produced about the Kriegsmarine U-boats in World War II, and further books and articles about the U-boats of that period are published frequently. It is difficult, however, to find comprehensive research about the build-up of the German U-boat Force and the training and exercise activities of the German U-boats during the period leading to the outbreak of WW II on 01 September 1939. Those familiar with the internet will end soon after punching in respective keywords in search-machines such as “Google” at just a few hits followed by numerous pages full of links to the literature, articles and pictures about the events in the U-boat war 1939-1945.

Since there are only few summarizing presentations about the first years of the U-boat Force of the Kriegsmarine, often only as introducing chapter in books about the U-boat war starting in 1939, one is forced to dig through older books and articles in newspapers and periodica such as “Köhler´s Flottenkalender”, “Nauticus” or those in the domestic and foreign press of these years, to establish some picture about the early years of the Kriegsmarine U-boats.

The following essay will provide a short overview about the conceptual framework, the build-up and the training as well as exercise planning for the young U-boat force of the Kriegsmarine before the outbreak of war. The activities outside homewaters shall be looked at as well, including port calls in foreign countries. Furthermore, the myth will be investigated, whether and to what extent the U-boats have been a part of the general war preparation of the German Reich under Adolf Hitler.

Armament Program

It is commonly known that the Versailles Peace Treaty of 28 September 1919 (in force as of 10 January 1920) granted the German Reich a Navy of just 15,000 personnel and a total tonnage of 144,000 t comprising all components of the fleet. Foremost, it denied the German Reich the development, construction and operation of U-boats. Notwithstanding, there were activities by the German Reich kept secret to maintain the existing capabilities to develop and construct U-boats, by and large outside Germany, e.g. in the Netherlands, Turkey, Finland and Spain. When the National Socialistic Party (NSDAP) took over government on 30 January 1933, the observation of many areas of restrictions of the Versailles Treaty started to faint, such as in the field of U-boat construction.

The new government soon supported initial plans for the creation of a U-boat Fleet of initially some 16 U-boats (eight 500 t and eight 800 t U-boats) drafted before January 1933 by the Reichsmarine of the German Weimar Republic, which were thought to be implementable by the Autumn of 1933. Notwithstanding, the creation of a U-boat Force was given a lower priority in the fleet construction program. Clearly, the focus was on building larger pocket battle ships and other surface units. This meant for the planned U-boat Force to concentrate on smaller 250 to boats during the initial phase, enabling to at least commission a sufficient number of units. Also, the possible operational employment of U-boats was restricted very much by the progress in the further development of the International Law of War.

U-1 im Baudock bei den Deutschen Werken Kiel 1935
U 1 under construction 1935 at Deutsche Werke Kiel Picture: German U-Boat Museum

Under the new regime, the creation of a U-boat Force was pursued in the open and much faster. As early as 02 February 1933 the establishment of a first submarine training facility was ordered at Kiel-Wik to be opened by 01 October 1933, interestingly enough under the harmless name “Anti-Submarine Warfare School”. At the same time, the construction of the first U-boats was to start at the Deutsche Werke shipyard at Kiel (DWK). Actually, not before the end of 1933 it was decided to erect a construction hall at DWK to disguise the building of new U-boats still under some secrecy, construction time per U-boat between 5 and 6 months. In May 1934 two more construction halls were added to the initial building order. Moreover, two more shipyards were included in the future family of U-boat construction shipyards, i.e. the Germania shipyard at Kiel and the Deschimag (AG Weser) at Bremen, both primarily for the possible construction of larger size U-boats of the Type I A and VII A. Although some considerable efforts went into preparation and procuring material required the measures intended were still kept secret until the end of 1934 due to political concerns (Germany seeking agreement with Britain on Naval relations with regard to the future fleet buildup). Eventually, all preparation had been advanced by February 1935 to such a degree that on 11 February 1935 keels were laid for the Type II A U-boats U 1 to U 6.

Multinational Naval Agreements

The buildup of a German U-boat Force, initially secret but from early 1935 more and more open, was to observe politically and conceptually the multinational Naval agreements resulting from the international policy of arms control and disarmament, such as the “Washington Naval Conference” of 1921/1922 and the “Geneva Conference” of 1927, although the latter a failure.

This required any strategic planning of submarines to strictly adhere to, in particular the “London Naval Agreement” of 22 April 1930 between the seapowers of the USA, Britain, Japan, France and Italy, as it ruled trade war by submarines to be executed only in compliance with the International Law of War at Sea, i.e. only in accordance with the rules of Prize Order. On 25 March 1936 that agreement was amended by the “Second London Naval Agreement” to include some provisions of arms control, but it reiterated the ruling about the submarine warfare to strictly observe the Prize Order at sea. This so-called “London Submarine Protocol” was signed by the German Reich on 23 November 1936, in the end there were 45 states to do so.

Besides these international Naval Agreements there was another bilateral agreement of great importance, which also had significant aspects of arms control, and which had some impact on the U-boat construction program of the German Reich, at least temporarily.

Following first approaches in November 1934 and the start of formal negotiations on 02 June 1935 a “Anglo-German Naval Agreement (A.G.N.A.) was signed on 18 June 1935 allowing the German Reich to build up a submarine fleet sized 45 % of the total tonnage of the British submarine fleet, but also offering an option to even go up to 100 % of the total British submarine tonnage. At the same time, this meant the end of the ban to Germany to develop, construct and operate U-boats as laid down in the Versailles Treaty of 1919. With that, a building plan for initially 36 smaller tonnage U-boats (exempt the Type VII U-boat U 32) was sanctioned, de facto in parts even retroactively. Eventually, the option offered in the A.G.N.A. to build U-boats up to 100 % of the total British submarine tonnage was taken by Germany and officially notified on 10 December 1938. On 17 July 1937 the A.G.N.A. was amended to include some provisions on the timely exchange of information about each partner´s fleet construction program. However, in the end, the agreement was given notice of termination by Germany on 26 April 1939. Thereafter, the further buildup of the German U-boat Force was carried out without any restriction.


On 29 June 1935 the Type II A U-boat U 1 was the First of Class to be commissioned by the Kriegsmarine. In rapid succession more U-boats of this class followed, the first 6 U-boats formed the training flotilla of the “Anti Submarine Warfare School” (later: “Submarine School”). Beginning with U 7 the formation of the first combat flotilla was initiated, allowing to stage already on 28 September 1935 a ceremonial commissioning of the U-Flotilla “Weddigen” (named after the famous Commanding Officer of U 9 of the Imperial German Navy, Otto Weddigen) at Kiel with initially three U-boats under the “Führer der U-Boote/ F.d.U. (= Commander Submarines), Captain Karl Dönitz.

The ceremony was even attended by the Chancellor of the German Reich, Adolf Hitler, who actually went on board U 7, with many pictures from his visit taken. Until the 01st of September 1939 the German U-boat Force grew to 57 U-boats commissioned (Types: 2 x I A, 6 x II A, 18 x II B, 6 x II C, 10 x VII A, 8 x VII B and 7 x IX), and several flotillas were formed from this inflow of U-boats.

Practice training, overseas port calls and combat readiness training

p177_1_03In his memoires written after the war, the first commander of the new U-boat Forces, Karl Dönitz, describes the years of the buildup of the force. A training policy had been published at a time when the “U-boat Training Group” with its 6 Type II U-boats was formed, same as the U-Flotilla “Weddigen” was commissioned on 28 September 1935 as first frontline squadron. The policy required each crew to practice a minimum of 66 underwater and 66 surface attacks, to be followed by life torpedo firings. Ideally, the training schedule to keep up the operational readiness required was to follow a three-year- cycle, with one year basic and advanced training, a second year of primarily exercising and a third year of large distance maneuvers outside homewaters, including calls at foreign ports. Conceptually the crews were to be fully familiar with the missions of reconnaissance, engagement against enemy Naval Forces by torpedoes, artillery and mines, as well as trade war in compliance with prize order.

Hitler an Bord U-7 am 28.09.1935
Hitler on board U 7 om 28/09/1935

Also, the “Group Tactic” (later known as “Rudel” or “Wolfpack” tactic) was developed and exercised consequently. Training of the new U-boats and their crews was thorough and tough, even severe incidents occurred occasionally. So, on 20 November 1936 in the Lubeck Bight in the Baltic Sea U 18 collided with the torpedo boat T 156 while in torpedo practice training, with the U-boat eventually sinking, killing 8 of the 20 men strong crew. The U-boat was raised from the sea ground on 28 November 1936, went through major repairs, to be put back to service not before 30 September 1937.

Combat Readiness Training

The Spanish Civil War opened up training opportunities to the young U-boat Force under conditions well beyond peacetime employment. We have outlined this in our article of November 2012 “German U-boats in the Spanish Civil War” published under “Series” and “Myths”. Following the special mission “Ursula” by U 33 and U 34 a total of 14 Kriegsmarine U-boats (U 14/ U 19/ U 25/ U 26/ U 27/ U 28/ U 29/ U 30/ U 31/ U 32/ U 33/ U 34/ U 35 and U 36) have seen deployments of several weeks each off the Spanish coasts, most of them in support of the international regime of embargo operations against the belligerent parties in Spain. Some U-boats were detached several times, and all U-boats were based temporarily at Spanish ports, such as El Ferrol, Cadiz, Huelva, Algeciras and even Ceuta in Northern Africa.


U 28 entering a Spanish port in 1937 Picture: Deutsches U-Boot Museum
U 28 entering a Spanish port in 1937 Picture: Deutsches U-Boot Museum

The training and exercise activities of the U-boats were an outflow of the conceptual objectives of the Kriegsmarine. On 27 May 1936 the Naval leadership issued a “Tentative Combat Directive for the Kriegsmarine”, which set the contribution of the Kriegsmarine when in war with the assumed opponents Soviet Union and France. Britain was not considered to be a potential enemy.

The plan outlined among other tasks that the U-boats were to operate against French sealines of communication in the Mediterranean. In the Autumn of 1936 a war game of the Naval Academy exercised the successful engagement of U-boats against French troop transports in the Mediterranean, allowing after 6 weeks to re-deploy the U-boats to the North Sea to unite with the remaining fleet to deny France blockading the North Sea. It was not before a war game of the Naval Staff on 12 April 1938 that an assumption came up any war with France might also see Britain joining. However, no concrete operational planning was activated for that case for the time being. On the other hand, these paper exercises revealed the firm intent of the Navy to prevent the U-boats from being restricted to mere operation in the North Sea, rather to aim for operation in the Atlantic Ocean and further into the wider oceans, and integrating these scenarios in the combat readiness training. On 18 June 1937 the Naval Staff issued a “Study of the Objectives of Naval Operations in Wartime 1937/ 1938”, which became the basis of the Kriegsmarine´s “Combat Instructions 1938” guiding also the combat readiness training of U-boats.

For the first time the “Group Tactics” against a practice convoy were tested during the “German Armed Forces Autumn Exercises” in 1937 in the Baltic Sea, as it became regular procedure during the first years in the war at sea. At the end of 1937 a request by Dönitz was denied by Hitler himself to carry out such maneuvers in the wider Atlantic Ocean with Type I and Type II U-boats, since Hitler did not want to endanger the employment of the Kriegsmarine in the Spanish Civil War by massing U-boats in the Atlantic Ocean off Spain.

Between 22 April and 05 May 1938 a large scale exercise was executed in the North Sea by U-boats of the 1st U-Flotilla (U 9/ U 13/ U 17/ U 19/ U 21 and U 23) and U-boats of the 3rd U-Flotilla (U 12/ U 14/ U 16/ U 18/ U 20/ U 22 and U 24) practicing the concept of “Guided Operations” in wide ranging reconnaissance and attack operations.

The Flag Officer Submarines, Captain Dönitz, observing exercises in 1938

In May 1939 another large scale Naval Exercise was carried out west of the Bay of Biscay and off the Iberian Peninsula, where the “Rudeltaktik” (= “Wolf Pack Tactics”) was practiced to a larger extent. 15 Type VII A and Type IX U-boats participated, plus an oiler, a freighter, a U-boat support ship and a command ship for the staff directing the exercise. During the “hot phase” of the exercise between 12 and 15 May 1939 the surface units simulated a convoy that had to proceed though a barrier line with a length of several hundred miles, which was guarded by 5 groups of 3 U-boats each. This exercise showed some further efforts necessary to improve the “Wolf Pack”-Operations, while Dönitz was generally satisfied with the results of the exercise.

In July 1939 there was another large scale exercise in the Baltic Sea, this time in the presence of the Commander-in-Chief German Navy, Grand Admiral Erich Reader. The experiences of this exercise, designed to practice tactics for the combat engagements by U-boats, were integrated to the “Commander´s Handbook” for Commanding Officers of U-boats, which guided their way of operational acting during their combat patrols in the first years of the war at sea.