The United Kingdom, Japan and the United States sign the <a href="https://en.wikipedia.org/wiki/London_Naval_Treaty" id="mwag" rel="mw:WikiLink" title="London Naval Treaty">London Naval Treaty</a> regulating <a href="https://en.wikipedia.org/wiki/Submarine" id="mwaw" rel="mw:WikiLink" title="Submarine">submarine</a> warfare and limiting <a href="https://en.wikipedia.org/wiki/Shipbuilding" id="mwbA" rel="mw:WikiLink" title="Shipbuilding">shipbuilding</a>.