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Information compiled from DICTIONARY OF THE FIRST WORLD WAR
by Stepehen Pope & Elizabeth-Anne Wheal, published by Pen & Sword ISBN 0 85052 979-4


Serious worldwide naval interest in ships that could travel underwater began in the mid-1880s, aroused by the development of self-propelling torpedoes. At first France led the world in the design and construction of steam-powered underwater boats, which fell into two broad categories: true submarines, cigar-shaped with a conning tower, were single-hulled vessels intended to travel only underwater and restricted to very short-range operations; boat-hulled ‘submersibles’ were longer-range surface craft that could dive underwater for a few minutes at a time.

The distinction was blurred in the work of independent US designer J. P. Holland, whose small Holland X (1901) was enclosed in two hulls, using air pumped between them to control buoyancy and underwater trim. The design set the standard for European navies, and by 1914 both Great Britain and Germany were producing relatively large, diesel-powered boats capable of long-range offensive patrol work.

Though slow, fragile, uncomfortable and able to dive for only a few hours at a time, the submarine was a potential threat to battlefleet orthodoxy, guaranteeing opposition from conservative naval leaders worldwide. Professional and public opinion also shared doubts about the moral acceptability of ‘underwater torpedo boats’. Every major navy had its enthusiasts for greatly expanded submarine forces, and all were interested in long-range ‘offensive’ boats, but none regarded their development as a major priority before 1914. The French NAVY possessed the world’s largest submarine fleet in August 1914, but few of its 123 boats were fit for military operations, and the service suffered from constant pre-war experimentations which precluded standardization and created severe maintenance difficulties. Failure to develop a reliable diesel engine meant that most long-range boats were steam-powered and dangerously slow to dive. Mechanical unreliability, poor periscopes, ill-positioned hydroplanes (for underwater stability) and restrictions on diving depth imposed by externally mounted torpedo tubes also hampered wartime performance.

French shipyards completed only 28 new boats in wartime (against 15 losses and dozens of retirements), and most Allied submarine development was carried out by the British, who engaged in series production of ever larger and more powerful craft. Britain had produced the first diesel-powered offensive patrol boats from 1909, and had 17 D- and E-Type vessels in service by August 1914, along with 40 older B- and C-Types for coastal operations.

The E-Type design, regularly improved and enlarged, was the mainstay of British wartime operations. Another 46 were built up to 1917 (including 6 minelayers), and overall production included a further 88 boats of various experimental types, culminating in giant ‘fleet’ submarines. With 137 serving boats at the Armistice and 78 more under construction, the Royal Navy possessed the largest and most successful Allied fleet, although it suffered 54 wartime losses, including 7 boats scuttled in the Baltic when German forces overran Finland in 1918.

The Russian Navy possessed 41 coastal submarines in August 1914, and some two dozen new boats were in service by late 1917, but their weapons and other equipment were generally inferior and they had little success, sinking only a handful of steamers and sailing craft in the Baltic and the Black Sea.

The Italian Navy had only 25 coastal boats by 1915, and material shortages meant that very little wartime construction was possible. Targeted against warships in the Adriatic and around the country’s long coastline, they shared the surface fleet’s logistic difficulties and scored no significant successes, against 7 boats lost.

Although the US Navy possessed 51 boats in 1914, none were suitable for long-range operations and most were obsolete. Expansion from 1915 produced a few long-range (L Class) boats over the next two years, and they served without loss or significant success on wartime anti-submarine patrols.

The Austro-Hungarian Navy possessed seven small coastal boats in August 1914, but only five were suitable for active service. No wartime production was possible, and six boats under construction were taken over by Germany in November 1914, but a few small German boats were sent in pieces to the Adriatic base of Pola and assembled for use by Austro-Hungarian crews. German submarines operating from Adriatic bases often flew the Austro-Hungarian flag to enable attacks on Italian shipping before Italy declared war on Germany. but Austrian successes were few.

The German Navy ultimately possessed the largest, most technically advanced and ambitiously deployed contemporary submarine service, but had no boats before 1906. Long-range diesel-powered boats were in service from 1913, but only 10 were available the following August, intended to operate against warships in the North Sea, while 18 older boats covered coastal defence and training.

The German Navy opted for series production of relatively few designs, with consequent benefits to maintenance, training standards and operational experience. Its best 1914 submarines had reliable engines, excellent periscopes, relatively efficient torpedoes and an operational range of up to 6,500km. A further 134 U-boats were operational in wartime, along with 132 small UB-boats and 79 minelaying UC-boats. All three types became steadily larger and more seaworthy, with a general slight increase in surface and submerged speeds, quicker diving times, better torpedoes, and bigger surface armament. Variations on basic designs included U-71 to U-80, built as long-range minelayers or supply ships, and massive ‘U-cruisers’.

Deployed against commerce and skilfully handled, German submarines came close to achieving decisive results in 1917, but the number of boats at sea (never more than 61) was insufficient to paralyse Allied maritime communications completely. Wartime losses were very high, with 192 boats sunk or interned before the Armistice and more than 5,400 crew killed.

Submarine Warfare

Pre-war naval strategists divided operational use of submarines into offensive and defensive categories. Defensive warfare involved coastal boats lying in wait against attacks on home ports or attacking warships engaged in close blockade. Most of the small submarines designed in the previous decade were capable of these short-range operations in 1914. Offensive submarine warfare —defined in 1914 as attacking warships further afield, ideally in or near their bases — was regarded by some naval leaders as intrinsically unethical, and by most as a major threat to battlefleet safety.

Except as a deterrent to surface attack, defensive coastal boats proved less important than expected in wartime. Close blockades were not generally attempted using warships, and coastal raids by surface ships were usually too fleeting to be caught by slow submarines.

Long-range offensive boats, sometimes towed to distant targets, were in their infancy, but the few suitable German and British submarines made an immediate wartime impression with their patrols in the North Sea and the Heligoland Bight, respectively, persuading the British Grand Fleet into temporary retreat on the northern Irish coast, and obliging the German High Seas Fleet to use the Kiel Canal for access to the western Baltic. An early rash of warship sinkings contributed to a generalized outbreak of ’periscopitis’ (the sighting of imagined submarines or their imaginary secret bases) that affected belligerent fleet commanders everywhere.

Wartime technical development was dominated by the British and German services, and both quickly recognized serious weaknesses in their performance against warships. Hostile fleets proved hard to find once at sea, and the reconnaissance value of submarines was further limited by lack of reliable long-range radio (the British were frequently required to use carrier pigeons). Warships could generally avoid submarine attack by zigzagging at high speed, and most early sinkings were made possible by failure to adopt rehearsed anti-submarine manoeuvres.

Submarines were also too slow for opportunistic action against fleets and had no surface guns in 1914, so that sighting by even small warships (unsuitable for torpedo attack) forced them to dive. Slow diving times, just over a minute for the best British boats but three to four minutes for U-boats, made any kind of contact with enemy fleet destroyers highly dangerous. The complex new technology of submarines was ill-suited to regular wartime operation. so that breakdowns and damage routinely reduced all sides to about a third of their nominal strength.

Submarine successes against warships never entirely dried up - the old British Pre-Dreadnought Britannia was sunk off Cape Trafalgar on 10 November 1918 — but became far less frequent as fleets were handled with increasing caution. The Royal Navy nevertheless maintained most of its best submarines with the Grand Fleet, and developed faster ‘fleet’ boats for the purpose. The German Navy generally kept only a few defensive submarines with the High Seas Fleet itself, but occasionally recalled large numbers to take part in fleet actions, usually stationing them off British bases to little effect.

The submarine’s reputation as a potentially decisive weapon was most amply fulfilled in its role as a commerce raider. Large-scale operations against supply and transport shipping became feasible once wartime experience demonstrated the long-range potential of modern boats. The British sent a few submarines into the Baltic and the Dardanelles with considerable success, and Russian Navy submarines sank one or two steamers, but from late 1914 the German Navy diverted its main submarine effort to Allied trade routes. Early German sinkings, and most Allied, were conducted under ‘prize rules’ -requiring a submarine to surface, search and warn any non-military target—but these rules were gradually abandoned as part of Germany’s all-out commerce campaign from early 1915.

The requirements of commerce warfare dictated the design and development of U-boats from 1915. Increased range and surface speed, faster diving times and better torpedoes were obvious requirements, but alternative weapons were needed to deal with smaller ships while conserving limited torpedo supplies. Surface guns steadily increased in size up to 150mm, but shells were bulky cargo and commanders preferred to scuttle small ships or sink them with explosive charges whenever possible.

German UC-boats were developed as minelayers, sinking more than a million tons of Allied merchant shipping, and small numbers of boats were adapted for the role by Allied navies. British (and French) boats were also regularly employed as anti-submarine craft - particularly in surface ambushes at destinations located by Room 40 intercepts - and were responsible for destroying 17 U-boats with torpedoes. The German Navy occasionally used Mediterranean U-boats to supply Senussi forces in North Africa, and submarines on all sides dropped or rescued agents behind enemy lines.

Last updated: 11 May, 2018

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