[citation needed] The British Royal Navy interned the defeated German High Seas Fleet in November 1918.

The Treaty of Versailles, signed a week later on 28 June 1919, imposed strict limits on the sizes and numbers of warships which the newly-installed German government had the right to build and maintain.

[3] US President Woodrow Wilson's administration had already announced successive plans for the expansion of the US Navy from 1916 to 1919 that would have resulted in a massive fleet of 50 modern battleships.

[9] At the first plenary session held November 21, 1921, US Secretary of State Charles Evans Hughes presented his country's proposals.

[10] The ambitious slogan received enthusiastic public endorsement and likely abbreviated the conference while helping ensure his proposals were largely adopted.

Britain could no longer have adequate fleets in the North Sea, the Mediterranean and the Far East simultaneously, which provoked outrage from parts of the Royal Navy.

[citation needed] Nevertheless, there was huge demand for the British to agree to the limits and reductions: the risk of war with the Americans was increasingly regarded as merely theoretical as there were very few policy differences between the two Anglophone powers; continued naval spending was unpopular in Britain throughout the empire; and Britain was implementing major budget reductions due to the post–World War I recession.

Japanese naval doctrine required the maintenance of a fleet 70% the size of that of the United States, which was felt to be the minimum necessary to defeat the Americans in any subsequent war.

[citation needed] His opinion was opposed strongly by Katō Kanji, the president of the Naval Staff College, who acted as his chief naval aide at the delegation and represented the influential "big navy" opinion that Japan had to prepare as thoroughly as possible for an inevitable conflict against the United States, which could build more warships because of its superior industrial might.

[12] Katō Tomosaburō was finally able to persuade the Japanese high command to accept the Hughes proposals, but the treaty was for years a source of controversy in the navy.

[13] The French delegation initially responded negatively to the idea of reducing their capital ships' tonnage to 175,000 tons and demanded 350,000, slightly above the Japanese limit.

In particular, the Japanese delegation was keen to retain their newest battleship Mutsu, which had been funded with great public enthusiasm, including donations from schoolchildren.

The limit proposed, of a 10,000 ton maximum displacement and 8-inch calibre guns, was intended to allow the British to retain the Hawkins class, then being constructed.

[18] Article XIX of the treaty also prohibited the British, the Japanese and the Americans from constructing any new fortifications or naval bases in the Pacific Ocean region.

That was a significant victory for Japan, as newly-fortified British or American bases would be a serious problem for the Japanese in the event of any future war.

That provision of the treaty essentially guaranteed that Japan would be the dominant power in the Western Pacific Ocean and was crucial in gaining Japanese acceptance of the limits on capital ship construction.

The tonnage limits defined by Articles IV and VII (tabulated) gave a strength ratio of approximately 5:5:3:1.75:1.75 for the UK, the United States, Japan, Italy, and France, respectively.

The keel laying of Jean Bart in December 1936, albeit less than three weeks before the treaty expired, increased the magnitude of France's violation by another 35,000 tons.

However, by the Zara-class cruisers in the late 1920s and early 1930s, it had abandoned all pretense and built ships that topped 11,000 long tons (11,000 t) by a wide margin.

The British Nelson class took advantage of the fact that the definition of tonnage excluded fuel and reserve boiler feed water.

His opinion was more complex, however, in that he believed the United States could outproduce Japan by a greater factor than the 5:3 ratio because of the huge American production advantage of which he had expert knowledge since he had served with the Japanese embassy in Washington.

After the signing of the treaty, he commented, "Anyone who has seen the auto factories in Detroit and the oil-fields in Texas knows that Japan lacks the power for a naval race with America."

"[27] He believed that other methods than a spree of construction would be needed to even the odds, which may have contributed to his advocacy of the plan to attack Pearl Harbor.

[28] What was unknown to the participants of the Conference was that the American "Black Chamber" (the Cypher Bureau, a US intelligence service), commanded by Herbert Yardley, was spying on the delegations' communications with their home capitals.