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ut these were a minority. See W. Holmes, Undersea Victory: the influence of submarines on the war
in the Pacific, Double Day: New York, 1966, p. 34. Also Allan Millett and Williamson Murray (eds.),
Military Innovation in the Inter War Period, Cambridge University Press: Cambridge, 1996, p. 259.
19. Holmes, Undersea Victory, p. 34.
20. Ronald Spector, Eagle Against the Sun, Free Press: New York, 1985, p. 482.
21. Millett and Murray, Military Innovation in the Inter War Period, p. 259.
22. Spector, Eagle Against the Sun, pp. 482-3. See also Montgomery Meigs, Slide Rules and Submarines,
National Defense University Press: Washington DC, 1990, pp. 154-6. Also Holmes, Undersea Victory,
p. 86.
23. Blair, Silent Victory, p. 361.
24. Blair, Silent Victory, pp. 446-7 and 818.
25. A key advantage for US submarines was the deployment of ‘SJ’ surface search radar, which most
submarines deployed by January 1943. The SJ was a directional radar, used to sweep the surrounding
sea for targets. The radar masts could also be extending above the water before surfacing, to check
the area for enemy warships and aircraft. This was considerably more effective than using the
periscope, particularly on dark nights. As the campaign progressed, more advanced radars were
fitted to submarines, which allowed fleet submarines to enjoy a considerable advantage in detection
over their Japanese adversaries. See Holmes, Undersea Victory, p. 194; and Norman Friedman, US
Submarines Through 1945: an illustrated design history, Naval Institute Press: Annapolis, 1995, pp.
235-8.
26. Without signals intelligence, submarine operations would have been more difficult and costly
because of the vast areas that had to be patrolled. Through intercept, cryptanalysis and translation
of Japanese messages, signals intelligence provided a constant flow of information on Japanese
naval and merchant shipping, convoy routing and composition as well as anti-submarine measures.
In addition to the direct results, there were equally as important indirect outcomes of signals
intelligence—an US analysis of signals intelligence in 1942 and 1943 provided additional proof
that magnetic torpedo exploders were not functioning properly. The process for disseminating
targetable information from these intercepts was streamlined by the Fleet Radio Unit, Pacific Fleet
and a daily report would be radioed to patrolling submarines at noon. See John Winton, Ultra in the
Pacific, Naval Institute Press: Annapolis, 1993, p. 192. See also Charles Lockwood, Communications
Intelligence Contributions to Submarine Warfare in World War 2, Special Research History 235, US
Navy, 17 June 1947: Department of the Navy – Naval Historical Center website, accessed 20 September 2011.
27. Spector, Eagle Against the Sun, p. 480.
28. During the interwar years, the US Navy saw the Japanese as a future enemy. Planners assumed that
any hostilities would start with a Japanese attack, followed by a wide-ranging naval conflict, with
the Japanese being slowly pushed back across the Pacific to their home islands by the weight of the
US Navy. At least initially, there was no role for submarines in connection with US fleet operations as
part of this scheme, although they might be used as scouts. Operations such as commerce raiding
would be carried out by light cruisers, not submarines, despite the lessons from German U-Boats in
the Atlantic during World War 1. Even had the US Navy sought to emulate this success in a future
war with Japan, there were no US submarines with the capability (especially range) to do so until the
mid-1930s. See Parrish, The Submarine, pp. 318-9.
29. Edward Miller, War Plan Orange: the US strategy to defeat Japan 1897-1945, Naval Institute Press:
Annapolis, 1991, p. 152.
30. Gunter Bischof and Robert Dupont (eds.), The Pacific War Revisited, Louisiana State University Press:
Baton Rouge, 1997, p. 91.
31. Miller, War Plan Orange, p. 319.
32. Richard Dean-Burns, ‘Regulating Submarine Warfare, 1921-41: a case study in arms control and
limited war’, Military Affairs, Vol. 35, No. 2, April 1971, pp. 58-9.
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