U-Boat: Germany's Submarines of WWI & WWII

The U-boat, short for Unterseeboot (undersea boat), was the name for submarines used by the German Navy during the First World War (1914-18) and Second World War (1939-45). In the two Battles of the Atlantic, U-boats sank thousands of ships, but defensive strategies such as dropping depth charges, providing air cover, and, above all, the convoy system, ensured Britain was supplied with the resources it needed to continue both wars until victory was achieved on land.

U-Boats in WWI

When WWI began in 1914, the German Imperial Navy had only 20 operational submarines or Unterseeboots (undersea boats), as they were known, a name soon shortened to U-boat. Together, Britain and France had around 200 submarines. German production went into overdrive to catch up. The German navy constructed several classes of submarines to meet different requirements, such as coastal patrols, laying mines, and long-distance vessels. By 1917, Germany had 140 U-boats. While the British Admiralty focused on smaller submarines for the defence of ports, Germany opted for a vessel that could attack enemy shipping anywhere at sea. U-boats became particularly important following the Battle of Jutland in May 1916 (a strategic victory for the Royal Navy, but one with high losses), after which the giant German battleships were largely confined to port. U-boats, on the other hand, were free to roam hidden beneath the waves and attack at will any enemy target they came across in the North Sea, Atlantic Ocean, and the coastal waters of the British Isles.

The earliest U-boats, the UB class, were limited to coastal operations, but developments improved their operational capacity as the war wore on. The typical WWI U-boat had a range capable of reaching the Western Atlantic Ocean, a top speed of 17 knots, and displaced around 700 tons. U-boats carried six torpedoes. Two torpedoes could be fired from the bow and two from the stern. The submarine also had a gun which could be fired when on the surface; this had a minimum calibre of 4.1 inches (10.4 mm). A diesel engine was used when on the surface, and twin electric engines when submerged. The crew on board numbered up to 39 persons. Conditions on board were extremely cramped and uncomfortable, and made worse by the constant stench of diesel fuel, which even permeated the taste of the submariner's food.

The German Navy built a larger class of U-boats, which was unarmed but capable of carrying cargo. The Deutschland was the first of this type, put in service in 1916. Some of these cargo submarines were subsequently converted into armed vessels known as U-cruisers, although the first were not operational until 1918. The U-cruisers had an impressive range of 12,000 nautical miles, and they could well have turned the tide of the war if they had been produced earlier and in larger numbers.

The UC-class submarines were used as minelayers from 1915. With a slow speed of six knots and a limited range of 750 nautical miles, these vessels were designed to stay near coastlines and lay mines, 12 per trip. The mines were released from near-vertical tubes that had been flooded. An upgrade to the class in 1916 increased the range tenfold and the mine load to 18. The UC II class was also armed with a 3.4-inch (8.8 cm) gun. The UE-class submarine was a larger, ocean-going version of the UC-class. The UE-boats, in service from 1915, could voyage 8,000 nautical miles and carry 34 mines. A class upgrade in 1918 meant the newer UE-boats could carry 42 mines in their tubes and another 30 in deck containers.

Read More