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.
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.
