U 151 class Submarine (1916)

German Cargo/Cruiser Submarines (1916-18): U-151, 152, 153, 154, 155, 156, 157.

SMS Deutschland was born SS Deutschland, a civilian registered, blockade-breaking German merchant submarine optimized for cago in World War I. Developed with private funds like Bremen, they were operated by the North German Lloyd Line, and became the first of six more U-151-class. After the two, used as unarmed cargo submarines for two voyages each as unarmed merchantman to the US they were converted by the German Imperial Navy on 19 February 1917 into U-155 and U-156 with torpedo tubes and deck guns, five more following, starting a raiding career far from home, including to the US shores. They were the first of the “U-Kreuzer” abbreviation for “submarine cruisers” a new and quite influential design.

Development

The blockade of Germany

The country name was carried by many generations of ships. In 1914, there was already an SMS Deutschland, and she was a German ferry commissioned as a minelayer during World War I. But also in 1914, it was clear that the British naval blockade of Germany, made easier by the Skagerrak strait and limited passages to the Atlantic from the north sea, all closely monitored, was established from the start and would last until November 1918, having grave effects on the population on the long run. Germany had blockade runners, standard cargo ships using other nationalities as disguise, but ships were often controlled in international waters. Blockades had been used in naval warfare since antiquity (and are more absolute than quarantines), so Germany tried out every possibility in its book. For ships, the most successful was “Marie” that successfully ran the British North Sea blockade and docked, albeit heavily damaged, in Batavia, Dutch East Indies on May 13, 1916. In 1917 Germany also tried unsuccessfully to supply their forces in Africa by sending the Zeppelin LZ104.

The blockade of Germany (1914–1918) was a major strategy of Allies led by the Royal Navy mostly, weakening Germany by cutting off its access to food, raw materials, and trade. Ships were controlled and prevented from reaching German ports via the North Sea. Germany still depended heavily on imports for food, fertilizer, and industrial materials so that strategy was aimed at crippling both its economy and civilian morale. The British navy controlled key sea routes, especially around the North Sea and ships heading to neutral countries like Netherlands or Denmark were still inspected to prevent goods from being re-exported to Germany, including for exampl ecotton, metals, and chemicals, all highly restricted ad confiscated if found after boarding.

Effects on Germany on the long run had severe consequences, especially for civilians with widesperad food shortages causing malnutrition and disease in particular in the harsh winter of 1916–1917, the infamous “Turnip Winter”. It is estimated by modenr historians that hundreds of thousands of German civilians died due to starvation and related illnesses. The blockade overall weakened Germany’s ability to sustain a long war, contributed to growing public unrest and declining morale and helped push Germany toward surrender in 1918. But it remained controversial as it targeted civilians as well as the military and continued even after the armistice in November 1918 for a time. Germany later cited it as an example of “unfair” Allied tactics. This fuelled also the resentment that pushed Hitler to power in 1933.

Germany tried out surface blockade runners desperately, usually fast merchant ships, sometimes disguised or sailing under neutral flags and equipped to be quickly converted into others if needed. Notable examples included SS Möwe, originally a merchant ship later turned armed raider, both blockade runner and attacking Allied shipping, captured or sinking dozens of ships, also bringing prizes back to Germany. Also SS Marie, seen above, one of several merchant vessels used to try to evade the blockade. She attempted to carry goods through neutral waters, often disguised. SS Rubens also attempted to run supplies, including war matériel to German East Africa but was intercepted by British forces and scuttled off the coast, though much cargo was salvaged.

They were Painted in neutral colors or disguised as foreign ships, used false flags and forged papers, had entire stocks of other flags and cloth colors to make more, a printing press and all the equipment to create bogus documentation, fake cargo on top on more strategic ones for inspections, but they also relied on speed, surprise, and weather conditions so captains were picked-up. They often sailed to or from neutral ports like those in Scandinavia close by, but had limited success compared to the submarines that were developed, as most, if not all, were intercepted by the Royal Navy. The very few that succeeded carried critical materials and boosted morale still, but it was a forlorn hope.

The Submarine Solution

It was clear in late 1914 that the early attempts at surfaced blockade running met a wall imposed by the Royal Navy. Crossing the Skaherrak or trying to slip to the North Sea was already problematic, so only Baltic destinations were realistically possible. At the time, many merchant ships of the large 1914 German merchant Marine rated at c5 million GRT, well below Britain at nearly 20 million GRT. Fast passenger liners and efficient cargo steamers with a strong global trade expansion until 1914 through major companies such as the Hamburg America Line and Norddeutscher Lloyd, but many were trapped in neutral ports once war began, including major liners in New York.

Some German merchant ships used as blockade runners still managed to elude Northern Patrol in poor visibility, heavy fog especially in the winter 1914-15 whereas foreign, neutral shipping was tempted by high prices offered by Germany to smuggle strategic materials such as rubber, cotton or metals, that could be hidden from inspection or listed as personal luggage. Some neutral ships collided aso by allowing themselves to be arrested by the Germans in Danish waters for bogus inspections. However, the desperation in Germany grew to provike a radical idea from the North German Lloyd Line.

One of the solutions discussed by late 1915 were already the U-Boat campaign in retaliation, and some thought an U-Boote could also carrying goods, and might be an ideal solution, provided it was large enough to make the transport of the most highly valued items worthwile, and had a solid underwater endurance to evade RN ships when spotted. So albeit this new naval weapon seemed well in the hand of the Kaiserliche Marine, it’s a trade company, the North German Lloyd Line, that first had the idea of a submarine used as cargo. The goal was to reach the United States, by then in good terms with Germany and with a large, sympathetic German-origin population on the west coast and hinterland.

However, designing a submarine to carry cargo between the United States and Germany and through the naval blockade of the Entente Powers, seems complicated and costly. But it could solve for German companies their major issues when trying to acquire raw materials that could not be found in quantity within the German sphere of influence, hindering the German war effort. Deutschland and Bremen were thus imagined and designed in early 1916 for the German Ocean Navigation, Deutsche Ozean-Reederei (DOR). This private shipping company was created specially for this enterprise, as a subsidiary company of the North German Lloyd shipping company (now Hapag-Lloyd) and financially backed by the Deutsche Bank.

To not be bothered by the Navy, and not having any issues entering neutral ports, they would not included any armament but the master specification would be their very wide beam to provide space for cargo, at first symbolically setup at 1,000 tonnes, until designers came to the conclusion that for the technology of the time, 700 tons was more realistic. Still, they could carry for example 230 tons of rubber in the free-flooding spaces between the inner and outer hulls, and other precious goods, making good their return on investmeent after just a few trips. There was relatively small space compared to surface ships, so only the most highly valued cargo would be considered. Investors believed they could recoup the boats’s construction after just two or three trips.

Order was passed on as early as 27 October 1915. Construction started at Flensburger Schiffbau for SS Deutschland, and Bremen in December 1915. It was not under military secret unlike Naval construction, but still, every effort to hide this construction was taken. This apparently never leaked to entente local contacts that Germany was building cargo submarines. Only when they became public, making their first trips, Britain and France protested, arguing that they could not be stopped and inspected for munitions. The US under diplomatic pressure for supposed German favoritism while neutral, later rejected the argument when the two made their first trip. For them, even submarines, if kept unarmed, could to be regarded as regular merchant vessels accordingly to treaties of the time (silent on this unforeseen development), permitting trade.

Construction of SS Deutschland led to a launching on 28 March 1916 and she was completed in late May or early June 1916, SS Bremen on 8 July 1916. Both soon departed for the US. Bremen however was lost on its maiden voyage to the United States. Deutschland made two trips, which were indeed profitable. But this was short lived. With the US entry into the war in April 1917 the other five submarine freighters planned, were all seized by the Kaiserliches Marine and converted into long-range cruiser submarine (U-kreuzers) with 150mm and 88mm deck guns, torpedo tubes and large torpedo reserves. Deustchland was the first converted, recommissioned on 15 February 1917, now registered U 151, leading of her own class of seven.

Design of the class

design and Construction at Flensburger Schiffbau

The following part will dwelve on both the civilian and military sides of the design. The company behind was obviously not Germaniawerft or Dantzig NyD and thus, had never build submarine before. Flensburger Schiffbau-Gesellschaft (Fensburg) was founded in 1872 by five shipowners and the yard delivered some 700 cargo ships, sail and steam, over decades. It ceased activity in 1990 and was resold. So by November 8, 1915, the Bremen merchant Alfred Lohmann (Lohmann & Co.), and shipping company Norddeutscher Lloyd (NDL), with agreement by the Deutsche Bank, founded the new Deutsche Ozean-Reederei GmbH (DOR) headquartered in Bremen.

They were to operate new cargo submarines and Flensburger Schiffbau was untrusted to the design and construction led by Chief Engineer Rudolf Erbach. The cost was enormous compared to a regular cargo shop, approximately 4 million marks including outfitting. Construction was maintained under some secret still, under the codename U 200, and in two stages to try to maintain secrecy as much as possible: First, the pressure hull was built under subcontract at the Flensburger Schiffbau-Gesellschaft shipyard, launched there on March 28, 1916 under the hull number 381. Since it still looked like conventional single hull, that did not attracted much attention. The final phase was under hull number 263 for the lead boat, SS deutschland, completed at the Friedrich Krupp Germaniawerft shipyard in Kiel, thus a military shipyards, with some experience with submarines.

Deutschland was to be the first of three merchant submarines. Bremen soon followed, then Oldenburg, built the same way. Only the first two of these three merchant submarines as delivered entered the regular German merchant registry under the tonnage certificate listed 791 GRT or 414 NRT. More were ordered, but all except Bremen, sunk underway, were taken over by the Navy and converted before their first deployment as merchant submarines. The more intense naval blockade, entry of the USA into the war and resumption of unrestricted warfare put and end to a commercial application for these grounbreaking submarines. So, in the end, three were built at Flensburg SB and completed at Germaniawerft, Kiel and the remaining five at Reiherstieg in Hamburg but completed also at Germaniawerft, Kiel. The first two were ready in mid 1916, but SS Oldenburg, later U-151 in January 1917 and the others from July to December the same year.

Hull and general design

The Deutschland class indeed were the largest submarines ever built in Germany, also in the world at the time (summer 1916). The next largest were the infamous British K-class “steam submarines” (1,980/2,566 tons) in late 1917 and further down the line the M-class of 1918 (1,594 tons/1,946 tons). It’s possible their tonnage differed before military conversion, but the final data accepted by all authors are the following: Deutschland displaced 1,512 t (1,488 long tons) surfaced and 1,875 t (1,845 long tons) submerged for a total of 2,272 t (2,236 long tons) when submerged and fully loaded.
Dimensions were unchanged after conversions. They were moderately long indeed at “just” 65 m (213 ft 3 in) overall, when the contemporary U-81 class measured 65.80 meters (225 ft). The pressure hull was standard for the time, with a spindle shape at both ends, 57 m (187 ft) in lenght, and 5.80 m (19 ft) wide. The magic happened with the unusually large outer hull that contained the cargo space at 8.90 m (29 ft 2 in) overall. The submarines had a draft of 5.30 m (17 ft 5 in) and a total height of 9.25 m (30 ft 4 in) from the keel to the top of the CT.