In the years after World War I, United States Navy planners
refined Plan Orange, the war plan designed to be employed in the event of a
conflict between the United States and the Japanese Empire. An Orange war was
expected to be “[an] offensive war, primarily naval, directed toward the
isolation and harassment of Japan, through control of her vital sea
communications and through offensive sea and air operations against her naval
forces and economic life.” As the planners learned more about Japan’s own plans
for fighting and defeating a superior US Navy, through the service’s radio
monitoring of Japanese fleet exercises and its deciphering of Japanese naval
codes, Orange Plan was revised to reflect these changing realities. The results
of these changes were then tested during the war games which were being
regularly played at the Naval War College in Newport, Rhode Island.
The Navy viewed the mission of its submarine force as being
to support the operations of the fleet. The main tasks for the submarine force,
therefore, were intelligence-gathering – observing the harbors of the Mandated
Islands – operations against the hostile main body, and assisting in the
defense of America’s principal Pacific bases in Hawaii and the Philippines, as
well as protecting the approaches to the Pacific side of the Panama Canal.
Surprisingly, since its war plan envisaged the eventual isolation of the
Japanese Home Islands, until late 1941 the US Navy did not contemplate the
early use of its submarines for major attacks against Japanese commerce. One of
the reasons for this omission, however, was the effect of international law. At
the London Naval Conference in 1930, Britain, the United States, and Japan had
signed a final agreement which contained an article outlawing the use of
unrestricted submarine warfare. Under Article 22 of the 1930 London Naval
Treaty, submarines were obliged to conform to the same rules of international
law as surface ships when it came to actions against merchant vessels.
Submarines were forbidden to sink a merchant ship without having first placed
its passengers, ship’s crew, and papers in a “place of safety.” This restriction
promised to limit severely the value of a sustained submarine campaign against
enemy commerce, since, among other things, it obliged the submarine to expose
itself to possible attack by remaining on the surface for a considerable period
of time, awaiting the transfer of the intended victim’s personnel to the
lifeboats or, indeed, taking them on board for delivery to a place of safety.
Top-level Navy thinking began to change on the issue of
unrestricted submarine warfare in early 1941, following the submission of a
study by the Naval War College which advocated the establishment of “war zones”
within which enemy merchant vessels could be sunk on sight. Although this
proposal was not accepted at that time, in May 1941 the Navy approved War Plan
Rainbow 5, which authorized the theater commanders to declare “strategical
areas” from which merchant ships would have to be excluded, thus incorporating
the essential feature of the earlier proposal. In late November 1941, the Chief
of Naval Operations, Adm. Harold R. Stark, drafted a cable giving the Commander
in Chief of the Asiatic Fleet authorization in the event of a formal war
between the United States and Japan to conduct unrestricted submarine and
aerial warfare in a specifically designated Far Eastern strategical area.
In December 1941, the United States Navy had 51 submarines
based in the Pacific. These boats were of two basic types – fleet submarines
and S Class submarines. The fleet submarines, most dating from the mid-1930s
and after, were of a number of different classes, ranging in size of from 271
to 381 feet (83 to 116m) in length and up to 2,730 tons in surface
displacement. With most of them having a wartime fuel capacity in excess of
90,000 gallons (341,000l), the fleet boats were capable of patrolling 10,000
nautical miles (18,500km) at normal cruising speed, without refueling. The
older S Class submarines, designed primarily for a defensive role and first
introduced into the fleet in the early 1920s, were 231 feet (70m) in length and
up to 950 tons in surface displacement. They lacked air conditioning, which
made submerged patrolling in tropical waters arduous for their crews, because
temperatures inside the boats could climb to 110 degrees Fahrenheit (45°C). In
addition, because the fuel capacity of the S Class submarines was far smaller –
less than a third of that of the newer fleet boats – their cruising range was
shorter.
At the time of the Japanese attack on Pearl Harbor, 29 of
the available US submarines in the Pacific Ocean – 23 fleet boats and six S
Class boats – were based in the Philippines. The other 22–16 fleet subs and six
of the S Class – were based at Pearl Harbor. On the morning of the attack,
however, there were only four submarines in Pearl Harbor, together with the submarine
tender Pelias. To the attacking Japanese aircraft, the submarines were not high
priority targets, and, as a result, none of them suffered significant damage in
the Japanese air raids. Five more Pearl Harbor-based subs were operating in
nearby waters that morning and were unaffected by the main attacks. The
submarines berthed at Cavite Naval Station in the Philippines were less lucky
than their Hawaiian counterparts. When the base was attacked by high-altitude
Japanese bombers on December 10, the fleet boat Sealion was wrecked beyond
repair and had to be scuttled, and her sister Seadragon was seriously damaged.
In the aftermath of the aerial destruction at Pearl Harbor,
which left all the battleships of the Pacific Fleet sunk or seriously damaged,
the submarines at Pearl Harbor and Cavite constituted one of the few offensive
forces left in the Pacific to slow down the Japanese onslaught. They were
rapidly put to use. Within six hours of the Japanese attack at Pearl Harbor,
well before the extent of the damage had even begun to be known, dispatch
orders from the Chief of Naval Operations to the affected commanders directed
“Execute unrestricted air and submarine warfare against Japan.” The first of
the Hawaiian-based subs left on a war patrol on December 11, 1941. Others
followed over the next two weeks. In all, four headed for operations around the
Marshall Islands, and three more left for petrols in the waters off the
Japanese Home Islands. Four other submarines from Pearl Harbor were already
operating off Midway Island and Wake Island. The Cavite-based subs were also at
sea, preparing unsuccessfully to defend the island of Luzon against invasion.
By December 11, 22 of the surviving 28 in the Philippines were operating in
waters to the east, west, and south of Luzon.
At the outbreak of the war, the Japanese merchant marine was
a choice target for attack. Because of a lack of adequate natural resources,
Japan had to import more than two-thirds of her basic requirements of iron ore,
petroleum, lead, tin, and manganese and all of her required nickel, wool, and
raw cotton. Each of the commodities arrived by ship. To meet her immense
transportation needs, Japan had some 6,400,000 tons of merchant shipping in
December 1941. Although prewar estimates had set a minimum requirement of three
million tons of shipping needed to keep Japan’s civilian economy going, initial
wartime requirements for the Japanese Imperial Army and Navy forced the
drafting of nearly four million tons of shipping for military purposes. This left
barely two-and-a-half million tons available to fulfil Japan’s domestic
economic needs.
From March 1942, the US submarines operated under one of two
commands: Commander Submarine Force, Pacific Fleet, headed (after January 1943)
by Vice Adm. Charles A. Lockwood at Pearl Harbor, and Commander Submarines,
Southwest Pacific (later Commander Submarines, Seventh Fleet), headed for much
of the war by Rear Adm. Ralph W. Christie, at Perth-Fremantle, Australia. The
Pearl Harbor-based submarines operated in the East China Sea and Empire waters
close to the Japanese Home Islands and off the Marshall, Marianas, Palau, and
Caroline Islands, with the Japanese fleet base at Truk a target of particular
interest. Hunting grounds for the Perth-based submarines included the South
China Sea, the Celebes Sea, and the Java Sea. Among the individual target areas
were Cam Ranh Bay and the waters off Manila, Davao (in the Philippines), and
Surabaya (in Java). Until the arrival of many additional submarines, however,
there were simply too many areas for the available boats to cover. As a result,
the deployed submarines were spread thin during all of 1942 and much of 1943.
US submarines were slow to take advantage of the promise
offered by Japan’s merchant shipping in the first months of the Pacific War.
For example, during the first three months of fighting, the subs sank only 13
Japanese merchant vessels. There were several important reasons for this
slowness. One was the conservative tactics used during the early patrolling. Based
on their pre-war training, submarine commanders were overly cautious in their
attacks on shipping targets – diving too quickly on the basis of contacts and
relying on submerged attacks at night rather than attacks on the surface.
Moreover, since the submarines operated singly, there was no chance to practice
team tactics to overcome resistance from Japanese escort vessels. With the
experience gained from their first few wartime patrols, though, most submarine
skippers learned to become more aggressive in attacking convoys, and the
sinking failures attributable to over-cautious tactics declined sharply.