Following World War I, the regulation of submarines was manifested in several signature developments that are discussed in this chapter. Following disarmament requirements in the Treaty of Versailles, the major powers further sought to limit armaments, especially submarines, through the negotiation of the 1922 Submarine Treaty and the 1930 London Naval Treaty. These agreements purported to restrict the number of submarines and other naval vessels held by any one State, but were ultimately unsuccessful. Also in the inter-war period, agreement was sought on the regulation of the Turkish Straits, with restrictions imposed on Turkey’s control over these waters and stipulating what vessels were allowed passage and under what conditions. Finally, the 1930 Hague Codification Conference entailed detailed discussions over the rights of warships, submarines and other vessels in the territorial sea. While this conference did not lead to the adoption of a treaty, the work achieved influenced subsequent codification efforts.