90 percent by sea - Defence Academy of the United Kingdom

the merchant ships themselves. Even so, there was never serious doubt as to what a navy
was for, rather, the argument concerned how it could best be achieved. As Mahan wrote in
1897: ‘The necessity of a navy…springs, therefore, from the existence of a peaceful shipping
[sic], and disappears with it’, 25 whilst 15 years later, Corbett agreed: ‘It is obvious that if the
object and end of naval warfare is the control of communications it must carry with it the right
to forbid, if we can, the passage of both public and private property upon the sea…To make
the position clear we should say ‘Commerce prevention’. 26 Even so, both Mahan and
Corbett agreed that commerce raiding was the tactic of the weak, an indecisive form of
warfare that could not defeat a nation with a strong navy, extensive mercantile fleet and
significant shipbuilding resources 27 - perhaps, their greatest miscalculation, given the events
of the subsequent World Wars. 28
The repeal of the Navigation Acts in 1849 also had seismic long term consequences for
British merchant shipping. Even so, Britain’s industrial advantage meant that by the turn of
the century, over 50 percent of all merchant shipping sailed under a British flag – 13 1/2
million gross tons - a staggering monopoly on the carriage of trade and a huge ‘invisibles’
earner for the British economy. 29 But newly industrialised nations began to catch up and by
the outbreak of the First World War, although tonnage had increased to nearly 19 million
tons, as a proportion, British flagged shipping had fallen to less than a quarter of the total. 30
However, British controlled oceanic carrying capacity was still impressive and represented a
huge strategic asset during the unrestricted submarine warfare of WW1. This threat had
been largely discounted by the pre-war Admiralty, who considered the submarine of limited
utility and unlikely to be able to locate and destroy dispersed shipping in the vastness of the
oceans. 31 Nevertheless, merchant shipbuilding declined during the inter war years and was
only re-invigorated with re-armament, with tonnage in 1939 approximately restored to 1918
levels. 32 Once again, despite the rapid re-introduction of convoying, British vulnerability to
commercial blockade was brutally exposed, with horrendous shipping losses peaking in
1941. The emphasis on the maintenance of supply routes was not confined to the Battle of
the Atlantic: for the allies, economic warfare was particularly effective in the Pacific theatre
against another island power, Japan, where American and British action was spectacularly
successful against Japanese merchant shipping – possibly the most decisive example of
Guerre de Course in history. 33,34
25 A Hattendorf, ed., Mahan on Naval Strategy, 28
26 Corbett, Some principles of Maritime Strategy, 91
27 Ibid., xiv
28 Ibid., xvi
29 Stewart, The Sea Our Heritage,43
30 Ibid
31 Ibid.,49
32 Ibid., 59
33 Translates as ‘War of Corsairs’ – the tactic of commerce raiding. Conducted by privateers in the 19 th Century
and submarines in the 20 th .
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