The 1922 Washington Treaty

In the decades before the Second World War, the international community made an unsuccessful attempt to avoid the looming conflict in the Pacific through an arms-control agreement that would limit the size and number of naval warships.

Delegates at the 1922 Washington Conference

In the aftermath of the First World War, the nine most powerful Pacific naval nations of the time (Britain, the United States, Japan, France, China, Italy, Belgium, Holland, and Portugal), met in Washington DC. (Germany, still under the terms of surrender that had ended the war, was not invited.) The newly-formed League of Nations had already proven itself to be mostly impotent, so the naval powers met on their own, at the request of US President Warren G Harding, to negotiate a series of arms-control agreements in an attempt to prevent something like the Great War from happening again. It was the first-ever international arms reduction treaty.

There were several issues that came to the table. The British Royal Navy was still the most powerful fleet in the world, and England still had colonies across the Pacific and Indian Oceans that she sought to protect, including India, Singapore, and Hong Kong. The United States had been a military non-entity before entering the war, but emerged as the second-most powerful naval force, behind Britain, with colonial holdings in the Philippines. France had been shattered during the war, but she still had colonial possessions in southeast Asia. Japan had been allied to the Entente during the war, but her geo-political goals were already diverging as she began a push to expand her influence into China, where both England and the US had their own interests. This led England, France and the United States to view the Japanese as rivals in the Pacific and as a potential threat to national security.

Hoping to prevent tensions in the area from exploding into another global conflict (and also hoping to spare themselves from the massive financial and industrial costs that would result from a naval arms race), the major powers hammered out a series of treaties. The first was the so-called Four-Power Treaty, signed in 1921. In it, Japan and England formally dissolved the alliance between them that had existed through the war. The agreement nominally called for a conference between all four nations (England, the US, Japan and France) if any of them should become involved in a military conflict, but this was a polite fiction: Britain had already decided that her national interests would be better served by an alliance with the United States to defend against potential Japanese expansion. The Pacific naval powers also agreed that they would not attempt to encroach upon any of each other’s colonial interests in the area.

The second pact, known as the Nine-Power Treaty, signed in 1922 by all of the conference participants, recognized the sovereignty and territorial integrity of China, and under the agreement Japan was obligated to return the Shandong province, which it had seized from Germany during the war, back to Chinese control. This was intended to remove most of the potential friction between Japan and the Anglo-Americans.

But the most important agreement was the Naval Treaty of 1922, which is also known as the Five-Power Treaty. This was negotiated by the largest naval powers (Britain, America, Japan, France and Italy), and although it was intended to ease tensions globally, it was primarily aimed at the Pacific region.

The Treaty set a series of limits on the amount and type of warships that could be deployed by the world’s largest navies. Capital ships (battleships and heavy cruisers) were to be limited to a maximum total tonnage set at a ratio of 5 to 5 to 3 between the British, Americans and Japanese, with France and Italy at a ratio of 1.75. In addition, each individual battleship was to be limited to 16-inch guns and a size of 35,000 tons each. Any ships in excess of these restrictions were to be decommissioned and dismantled, and no new capital ships could begin construction until 10 years after the Treaty was signed—and they had to be met by reduction in existing ships to stay within the mandated tonnage limits.

Since aircraft carriers were still new and had never really been tested in combat, they were viewed as less dangerous “auxiliary vessels” and were only a secondary concern, so the Treaty set few individual limits on them; they too were restricted in total tonnage at the same ratio as battleships. Each carrier could be no larger than 27,000 tons, however, with the exception of two existing capital ship hulls (battleship or cruiser) that could be re-converted into carriers no larger than 35,000 tons each. Further, small aircraft carriers of less than 10,000 tons would not be counted towards the total tonnage restrictions.

Finally, all parties agreed not to construct any more naval bases anywhere in the Pacific, or to expand its existing ones.

Each nation had portions of the treaty that it did not like. During negotiations, the British pushed for a global ban on submarines, but the French objected to this, and in the final draft there were no restrictions placed on them. Also left unregulated were light cruisers and destroyers, since nobody could reach any agreement on numbers of those ships to be allowed.

France was not happy with the numerical restrictions placed on its fleet (they fought to have numerical parity with Britain), but agreed to give up part of its capital ships in exchange for being allowed to construct submarines. Italy, on the other hand, successfully argued that it should have numerical parity with France (though in reality the Italians, with their far weaker industrial base, were never able to construct that many ships).

Most of the objections came from Japan, who rightly concluded that the treaty terms were intended specifically to limit her ability to reach combat parity with the Anglo-Americans. Japan argued for a 5:4 or 10:7 ratio instead of a 5:3, which, since the American and British fleets would be divided between the Pacific and Atlantic Oceans, would give Tokyo local superiority in any naval conflict. Japan was also not happy with the limits placed on individual battleship size and armament. But in the end, the Japanese decided that an unrestricted naval arms race with the United States would be unwinnable because of the massive American economic and industrial potential, and agreed to accept the limits specified in the Treaty. The United States, meanwhile, had broken the diplomatic codes of all the participating nations and knew their entire negotiating strategy, enabling the Americans to hold out for the minimum terms that Tokyo, in particular, would find acceptable.

Throughout the 1920s, all sides remained within the Treaty (mostly), busily cancelling or dismantling their excess ships. The treaty also had the side effect of changing the composition of the major military fleets, as prohibited battleships were dropped and less-regulated aircraft carriers were built instead.

But as international tensions grew in the early 1930s, ruptures appeared. Italy began building its Littorio-class battleships, which exceeded their permitted size, and the French Navy built two Dunkerque-class battleships, which exceeded the total tonnage restrictions. The American Lexington-class aircraft carriers, made from converted battleship hulls, exceeded the individual size restrictions. In Japan, objections to the treaty terms led to the rise of an ultra-nationalist faction within the military which called for a buildup of naval forces that would fuel aggressive expansion in Asia. The new Mogami-class heavy cruisers were built outside of the treaty restrictions, which led to diplomatic protests from the United States.

In late 1934 Tokyo gave formal notice that it would not renew the Washington Treaty once it expired in 1936, and began construction of a wave of new battleships and carriers, including the three planned “super-battleships” Yamato, Musashi and Shinano, the largest warships in the world. And knowing that the United States and Britain were the only nations with the naval power to stop them, the Japanese militarists began planning for a war with both. In the end, then, the Washington Treaty was a failure, and it would set the Pacific on the path to war.