There were three major international naval conferences in London, the first in 1908-09, the second in 1930 and the third in 1935. The latter two, together with the Washington Naval Conference in 1921-22 and the Geneva Conferences (1927 and 1932), resulted in agreements between the major powers on navy vessel numbers, armaments and the rules of engagement in the inter-war period.

The first conference was a continuation of the debates of the 2nd Hague Conference, with Britain hoping for the formation of an International Prize Court. Ten nations sent representatives, the main naval powers of Europe and the United States and Japan. The conference met from December 4, 1908 to February 26, 1909. The agreements were issued as the Declaration of London, containing seventy-one articles it restated much existing international maritime law. Unfortunately, the signatories' governments did not all ratify the Declaration and it never went into effect. During WW I the neutral United States pushed for the major antagonists to respect the treaty, hoping that the good protection in the Declaration for neutral vessels would be enforced.

The London conference of January 21 to April 22, 1930 was concerned with the agreements reached in Washington in 1922. Britain, the US, France, Italy and Japan attended. The major change was in battleship tonnage, altering the ratio between Britain, the US and Japan from 5:5:3 to 10:10:7, France and Italy excluded themselves from the new ratio agreement. All five agreed to a five-yar halt to capital ship construction, tighter controls on submarine warfare, and the continuation of limits on aircraft carriers. The next meeting was planned for 1935.

The December 1935 meeting was held with the treaties having a year to run. It marked the effective collapse of the controls, as Japan withdrew from the agreement after her requests for parity in naval power with the big two were rejected. The remaining powers signed a weak agreement on tonnage and Britain, France and the US agreed a ratio of construction. All five powers were constructing vessels violating the agreements by 1938.