Ten interesting facts about the Washington Naval Treaty

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Matthew Wright

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I'm a New Zealand historian with a life-long interest in matters military, particularly naval engineering. My books have principally been published by Penguin Random House. I'm a Fellow of the Royal Historical Society at University College, London.
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The ‘ Washington Naval Treaty ’ was one of the world’s few successful naval limitation agreements. It was negotiated between November 1921 and February 1922, in Washington, and signed on 6 February that year.

naval treaty
HMS Rodney after refitting at Liverpool, 1942 – a ship built as a direct outcome of the Five Power Treaty signed in Washington twenty years earlier. Public domain, via Wikipedia.

It limited not just numbers of ships, but also the specifications and timing of new-build vessels, but what’s perhaps more interesting is the diplomatic turning and twisting around it – and some of the curious quirks that followed in the terms, along with the actual costs and consequences:

1. ‘Washington Treaty’ is the common term for the agreement. But actually it’s a metonym – the use of a place-name to describe something associated with it, in this case the ‘Conference on the Limitation of Armaments’ held in Washington during the northern winter of 1921-22. The naval document was formally the ‘Five Power Treaty’, sometimes referred to officially as the ‘Washington Naval Treaty’ or ‘Naval Treaty’. It was only one of several agreements reached at the Conference. Other treaties negotiated at the same conference included one between five nations to limit submarines and poison gas; the Pacific Treaty, signed by the British Empire, United States, Japan and France, which replaced the Anglo-Japanese Alliance; the ‘Nine Power Treaty’ relating to customs tariffs in China; and the Shantung Treaty, between China and Japan.

2. Britain sent a team of naval architects to back their delegates Arthur Balfour, Lord Lee of Fareham and Sir Auckland Geddes. This meant the British negotiators could get expert advice more quickly than other parties.

3. The United States had access to other nations’ diplomatic codes, meaning they were able to obtain negotiating details the delegates referred back to their governments, including the Japanese bottom line.

4. The ‘Five Power Treaty’ remains one of the few successful naval arms limitation treaties, (mostly) followed by signatories and never repudiated before expiry.

5. The Treaty definition of ‘standard’ displacement took the form it did because the British didn’t want to reveal the existence of their secret liquid-loaded anti-torpedo system.

6. The Treaty also limited the extent to which heavy ships could be rebuilt – allowing a maximum increase of only 3000 tons, more deck armour, but no new side armour or alteration to main armament. This was to prevent anybody drastically improving the military characteristics.

7. The French version referred to battleships and battlecruisers as ‘ships of the line’; a quirk of language and nomenclature.

8. Existing, planned or under-construction capital ships scheduled for cancellation or scrapping totalled 845,740 tons, of which over 400,000 tons were British. Their agreed scrapping list included two pre-dreadnoughts.

9. Cancellations of part-built ships included US vessels on which the US Navy had spent $332 million to that time (in early 1920s money).

10. Britain was allowed to build two new battleships. However, these had to be to Treaty limits. What the Royal Navy really wanted was two of their planned 48,000-ton ‘G3’ class battlecruisers, but that was turned down.

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Copyright © Matthew Wright 2017




  1. A minor issue with your first ‘fact’ – the Washington Naval Treaty was formally the “TREATY BETWEEN THE BRITISH EMPIRE, THE UNITED STATES OF AMERICA, FRANCE, ITALY AND JAPAN LIMITATING NAVAL ARMAMENT” – the term ‘Five Power Treaty’ does not appear anywhere in the document.

    • The name I used is correct to the legal record I consulted: https://atojs.natlib.govt.nz/cgi-bin/atojs?a=d&cl=search&d=AJHR1922-I.——-10–1——0washington+treaty–

  2. I can’t see the term ‘Five Power Treaty’ anywhere in that document. In fact it uses the same title I did above. Am I missing something?

    The term ”Five Power Treaty’ was used informally a the time, but it was never a formal title.



    • Hi David, if you check carefully you’ll see the document I referred to has a different title from the one you cite: it refers to the “Treaty between the United States of America, the British Empire, France, Italy and Japan for the Limitation of Naval Armament”, which has a different order of countries. Countries in your order are given both on the Navweps site and in an Australian online version of the original document, here: http://www.austlii.edu.au/au/other/dfat/treaties/1923/9.html – but not in the reference I sent.

      I actually put a good deal of research into this issue for the article. In terms of the Salmond report I cited (which I regard as more accurate than the Australian online transcription, because it is in original print form and correlates with the US version discussed, e.g. on JSTOR https://www.jstor.org/stable/2213014?seq=1#page_scan_tab_contents ), the references to the five powers are on pp 3, 6 and 8. This was the first reference I have seen to ‘five powers’, which produced the formal title ‘Five Power Treaty’ as cited in other sources I also consulted, notably, the formal US ratification document, where it is given in the first instance along with a clarifying phrase (to avoid confusion with the other five power agreement signed at the Washington conference): https://www.loc.gov/law/help/us-treaties/bevans/m-ust000002-0351.pdf This underscores the status of the phrase, and it is also referenced as the formal name of this treaty in my other sources, e.g. the State Department archive: https://2001-2009.state.gov/r/pa/ho/time/id/88313.htm and this: https://www.globalsecurity.org/military/world/naval-arms-control-1921.htm, and this: http://totallyhistory.com/washington-naval-conference/ , also this http://www.u-s-history.com/pages/h1355.html and this: http://www.digitalhistory.uh.edu/disp_textbook.cfm?smtID=3&psid=3995 – all of which refer to it by this term. The online Britannica also has a useful summary here: https://www.britannica.com/event/Washington-Conference-1921-1922#ref227917

      What was going on? As is clear from these and other sources, including my own reference library, the conventions around nomenclature were complex and often variable between nations. You will note, for example, that Salmond simply refers to the ‘Naval Treaty’ in short form. However, the point is that as I understand it, the title given on the original 1922 treaty document was given a formal short form of ‘Five Power Treaty’ for diplomatic and legal purposes, which was in line with convention of the day; and that this became its formal title in that context, often referenced as such in documents, diplomatic and scholarly histories, sometimes to the exclusion of the other terms it received. At the same time, it was also known as the ‘Washington Treaty’ in naval construction circles, and has since gained that short name among naval enthusiasts for whom the other arms-limitation treaties of the same conference (which the diplomatic terms were designed to differentiate) fell into obscurity.

      You will appreciate that in a short article of this kind, a discursive approach to history that might explore these issues has to be replaced with a single word or two that sums up complex issues, including the formal name adopted for diplomatic purpose. It seemed reasonable to me that the adjective ‘formal’ was a fair and accurate way of doing that. I could have written ‘known as’, which might have averted any issue from your perspective because it doesn’t have the same implication. It purely came down to decisions over how to effectively summarise this quite complex naming system and the role of the term ‘Five Power Treaty’ as a formal title in most of my references. I hope that clarifies the point, which I’m not able to discuss further – I’ve gone to some length on reply because this issue is, and should be, reasonably discussed and outlined because it’s a common one when trying to summarise complex material. But you’ll appreciate that it is also a very minor matter, and I’ve really put all the time into it that I can reasonably devote at this stage.


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