The Second London Naval Treaty

On 25 March 1936 in London, representatives of the United States, Britain – and separately of Canada, Australia, New Zealand and India – and France signed the Treaty for the Limitation of Naval Armament, known as the Second London Naval Treaty. It was intended to replace the Washington Treaty of 1922 and the London Treaty of 1930, which expired at the end of 1936, and to remain in force until the end of 1942. Yet it was only a shadow of its predecessors. It no longer laid down how many warships each state might have, only how large and how heavily armed newly built vessels could be. Japan, the world’s third naval power, had walked out of the conference in January, and Italy, under League of Nations sanctions for its attack on Ethiopia, refused to sign. The treaty is commonly summed up as having been signed by the United States, Britain and France, but not by Japan and Italy. It should be added that Japan did not refuse to sign on the day of signature; it had broken off the talks two months earlier.

A conference without Japan

The London Treaty of 1930 obliged the powers to meet in 1935 and draw up a new agreement. Preliminary talks in the autumn of 1934 produced nothing, and on 29 December 1934 Japan denounced the Washington Treaty. Even so, the British government convened a conference of the five powers, which opened in London on 9 December 1935. Britain was represented by the First Lord of the Admiralty, Bolton Eyres-Monsell, and by the Foreign Secretary, a post to which Anthony Eden was appointed on 22 December after the collapse of the Hoare–Laval plan. The American delegation was led by Norman Davis, accompanied by the Chief of Naval Operations, Admiral William Standley. Japan was represented by Admiral Osami Nagano and Italy by its ambassador in London, Dino Grandi.

Nagano brought the same programme that Isoroku Yamamoto had presented in London a year earlier. Japan demanded a common upper tonnage limit for all the powers – in other words, parity with America and Britain – and proposed that these limits be as low as possible and that offensive weapons, above all battleships and aircraft carriers, be restricted or abolished. The Americans and British rejected the demand, convinced that parity in tonnage would give Japan superiority in the western Pacific. On 15 January 1936 the Japanese delegation announced its withdrawal from the conference. From that moment there was no chance of quantitative limits: no one wanted to restrict their own fleet when the world’s third naval power could build without restriction.

The conference took place in an increasingly poisonous atmosphere. The Italo-Ethiopian war was under way, and Italy, subject since November 1935 to League of Nations sanctions that Britain and France had helped to frame, had no intention of signing any undertakings with them. In Tokyo on 26 February 1936 young army officers attempted a coup d’état. On 7 March, while the talks were in session, Hitler sent troops into the demilitarised Rhineland. Germany did not take part in the conference, but its fleet was already limited by other means: in June 1935 Britain had concluded a naval agreement with it allowing a fleet equal to 35 per cent of the British one.

What the treaty laid down

The treaty restricted only the characteristics of new warships. A battleship could displace at most 35,000 tons standard, as under the Washington Treaty, and its guns could not exceed 14 inches, that is 356 mm. The British wanted this limit; the Americans were reluctant. At their insistence a so-called escalator clause was added: if Japan and Italy, as signatories of the Washington Treaty, did not accept the 14-inch limit by 1 April 1937, the calibre would revert to 16 inches (406 mm). An aircraft carrier could displace at most 23,000 tons, and a submarine 2,000 tons with guns of up to 130 mm. New light cruisers could not exceed 8,000 tons, and the construction of new heavy cruisers with 203 mm guns was forbidden unless another state threatened a signatory’s security. The parties undertook to inform one another of their building programmes. Article 25 allowed the limits to be set aside if a state outside the treaty built warships larger than it permitted.

The treaty also confirmed Article 22 of the 1930 treaty, which required submarines to observe the same rules towards merchant ships as surface warships, and called on other states to accede to this rule. In November 1936 it was set down in a separate London Protocol, to which Germany, Italy, Japan and the Soviet Union, among others, eventually acceded. In 1937 Britain concluded separate naval agreements with Germany and the Soviet Union extending the treaty’s qualitative limits to them.

The clauses that devoured the treaty

The safeguard clauses soon proved more important than the limits. Japan refused to commit itself to 14-inch guns, so from April 1937 the 16-inch calibre applied. Rumours that Japan was building battleships larger than the treaty allowed, which Tokyo would neither confirm nor deny, led the three powers to invoke the safeguard clause. On 30 June 1938 they signed a protocol raising the displacement limit for battleships to 45,000 tons. The rumours were true, and the reality exceeded them: at Kure the Yamato was being built, a ship of more than 60,000 tons with 460 mm guns.

Paradoxically, the treaty constrained almost exclusively the future Allies. The British, who in 1936 needed new battleships quickly, designed the King George V class within the limit, with 356 mm guns, and did not change the design when the limit was raised, as that would have delayed construction by a year and a half. The American North Carolina-class battleships, originally designed for 14-inch guns, received 406 mm guns once the clause had been invoked, but their armour still corresponded to the weaker shells. The next class, the South Dakotas, still kept within 35,000 tons at the cost of cramped conditions. Only the Iowa-class battleships, ordered in 1939, took advantage of the new limit. Meanwhile Germany was building the Bismarck-class battleships, which had a declared displacement of 35,000 tons but in reality exceeded 40,000, and Italy the Littorio-class ships, which were likewise heavier than stated.

The end of naval disarmament

The Second London Treaty closed the period that had begun in Washington in 1922. For fourteen years the naval powers had managed to negotiate about their fleets and agree on their size. From 1937, when the quantitative limits expired, each built as much as it could and wished. Japan expanded its fleet in secret, and in August 1936 its government adopted principles of national policy that, alongside preparations for war against the Soviet Union, envisaged expansion to the south, towards the South Seas, and the building of a fleet capable of standing up to the United States. Britain accelerated its rearmament, torn between the Japanese threat in Asia and the German and Italian threats in Europe. Stanley Baldwin’s government announced a programme of naval expansion in 1936, but there was not enough money or shipyard capacity for everything at once. The United States, after the Acts of 1938 and 1940, began building a fleet that during the war would come to exceed all the others put together.

Formally the treaty was to remain in force until the end of 1942, but after the outbreak of war in September 1939, when Britain and France suspended its application, it ceased to have any significance. Only the rule of the submarine protocol survived. During the war none of the belligerents observed it, and when Admiral Karl Dönitz was tried at Nuremberg, the tribunal found that the German navy had violated it but imposed no penalty on him for this, since the Allied navies had acted in a similar way. The last pre-war treaty on naval armaments was thus signed by states that wished to preserve the existing order, while those that intended to overthrow it remained outside.