in Singapore Graving Dock, August 1940|alt=An ocean liner, viewed from aft and above, sits in a dry dock. The Singapore strategy was a series of war plans that evolved between the wars in which the basing of a fleet at Singapore was a common but not a defining aspect. Some plans were designed to defeat Japan, while others were to deter aggression. In November 1918, the Australian
Minister for the Navy, Sir
Joseph Cook, had asked Admiral
Lord Jellicoe to draw up a scheme for the Empire's naval defence. Jellicoe set out on a tour of the Empire in the
battlecruiser in February 1919. The strategy was presented to the Dominions at the
1923 Imperial Conference. The authors of the memorandum divided a war with Japan into three phases. In the first phase, the garrison of Singapore would defend the fortress while the fleet made its way from home waters to Singapore. The fleet would sail from Singapore and relieve or recapture Hong Kong. The final phase would see the fleet blockade Japan and force it to accept terms. Estimates of the time for the fleet to reach Singapore after the outbreak of hostilities varied. It had to include the assembly of the fleet, preparations for the voyage and transit to Singapore. The first estimate was 42 days, assuming reasonable warning. In 1938, it was increased to 70 days, with 14 more for provisioning. It was further increased in June 1939 to 90 days plus 15 for provisioning and in September 1939, to 180 days. Oil storage facilities were constructed at
Gibraltar, Malta,
Port Said,
Port Sudan,
Aden,
Colombo,
Trincomalee,
Rangoon, Singapore and Hong Kong. A complicating factor was that the battleships could not traverse the
Suez Canal fully laden, so they would have to refuel on the other side. Singapore was to have storage for of oil. Secret bases were established at
Kamaran Bay,
Addu Atoll and
Nancowry. It was estimated that the fleet would require of oil per month, which would be transported in sixty
tankers. Oil would be shipped in from the
refineries at
Abadan and Rangoon, supplemented by buying the entire output of the Netherlands East Indies. The third phase received the least consideration but naval planners were aware that Singapore was too far from Japan to provide an adequate base for operations near Japan. The further the fleet proceeded from Singapore, the weaker it would become. The idea of invading Japan and fighting its armies was rejected as impractical but the British planners did not expect that the Japanese would willingly fight a decisive naval battle against the odds. They were therefore drawn to the concept of a blockade; from experience they were aware of the impact it could have on an island nation at the heart of a maritime empire and felt that economic pressure would suffice. Japan's vulnerability to blockade was studied; with information from the
Board of Trade and the
naval attaché in Tokyo, the planners estimated that the British Empire accounted for around 27 per cent of Japan's imports. In most cases these imports could be replaced from sources in China and the United States. Some critical materials for which Japan relied heavily on imports were identified, including metals, machinery, chemicals, oil and rubber and many of the best sources were under British control. Japanese access to neutral shipping could be restricted by refusing insurance to ships trading with Japan and by chartering ships to reduce the number available. Enforcement of a close naval blockade would make ships vulnerable to attack by aircraft and submarines. Blockading Japanese ports with small ships was a possibility but this would require the destruction or neutralisation of the Japanese fleet and it was far from certain that the Japanese fleet would place itself in a position where it could be destroyed. A plan was adopted for a more distant blockade, whereby ships bound for Japan would be intercepted as they passed through the
East Indies or the
Panama Canal. This would not cut off Japanese trade with China or Korea and probably not with the United States. The effectiveness of such a blockade was therefore questionable. The MNBDO had a strength of 7,000 and included a
brigade of
anti-aircraft guns, a brigade of
coastal artillery and a
battalion of infantry, all drawn from the
Royal Marines. In one paper exercise, the Royal Marines occupied
Nakagusuku Bay unopposed and the MNBDO constructed base from which the fleet blockaded Japan. Fleet exercises were conducted in the Mediterranean in the 1920s to test the MNBDO concept. The Royal Marines were not greatly interested in
amphibious warfare and lacking organisational backing, the techniques and tactics of amphibious warfare began to atrophy. By the 1930s the Admiralty was concerned that the United States and Japan were well ahead of Britain in this field and persuaded the Army and RAF to join with it in establishing the
Inter-Service Training and Development Centre, which opened in July 1938. Under its first commandant, Captain
Loben Maund, it began investigating the problems of amphibious warfare, including the design of
landing craft. In the 1920s, Colonel the
Master of Sempill led the semi-official
Sempill Mission to Japan to help the Imperial Japanese Navy establish an air arm. The Royal Navy was the world leader in naval aviation and the Sempill mission taught advanced techniques such as carrier deck landing, conducted training with modern aircraft and provided engines, ordnance and technical equipment. Within a decade, Japan had overtaken Britain. The Royal Navy pioneered the armoured flight deck, which enabled carriers to absorb damage but this limited the number of aircraft that a carrier could operate. The Royal Navy had great faith in the ability of ships' anti-aircraft batteries and saw little need for high performance fighters. To maximise the benefit of the small numbers of aircraft that could be carried, the Royal Navy developed multi-role aircraft such as the
Blackburn Roc,
Fairey Fulmar,
Fairey Barracuda,
Blackburn Skua and
Fairey Swordfish.
Fleet Air Arm aircraft were no match for their Japanese counterparts. The possibility of Japan taking advantage of a war in Europe was foreseen. In June 1939, the
Tientsin Incident showed that Germany might take advantage of a war in the Far East. In the event of war with Germany, Italy and Japan, two approaches were considered. The first was to reduce the war to one against Germany and Japan only by knocking Italy out of the conflict as quickly as possible. The former First Sea Lord, Sir
Reginald Drax, who was brought out of retirement to advise on strategy, called for a "flying squadron" of four or five battleships, along with an aircraft carrier, some cruisers and destroyers, to be sent to Singapore. Such a force would be too small to fight the Japanese main fleet, but could protect British trade in the Indian Ocean against
commerce raiders. Drax argued that a small, fast force would be better in this role than a large, slow one. When more ships became available, it could become the nucleus of a full-sized battle fleet. Chatfield, now
Minister for Coordination of Defence, disagreed with this concept. He felt that the flying squadron would become nothing more than a target for the Japanese fleet. Instead, he proposed that the Mediterranean be abandoned and the fleet sent to Singapore. == Base development ==