Japan joins the Pact of London

On 19 October 1915 the government of Japan acceded to the Pact of London, the declaration signed on 5 September 1914 by Britain, France and Russia. In it the three powers had undertaken not to conclude a separate peace during the war and that none of them would put forward peace terms without the consent of the others. Now Japan accepted the same obligation. This declaration should not be confused with the secret Treaty of London of April 1915, under which Italy entered the war.

An ally without obligations

Japan had been fighting Germany since August 1914, but formally it was bound to the Entente only by its alliance with Britain. Nothing prevented it from concluding a separate peace as soon as it had achieved its aims: it had taken Tsingtao and the German islands in the Pacific. Berlin tried to exploit this and through intermediaries sounded out the Japanese about leaving the war. Tokyo informed its allies each time, but in London, Paris and Petrograd people still wondered how far Japanese loyalty went. Japan refused to send troops to Europe, and at the same time was imposing its “Twenty-One Demands” on China.

For a long time the foreign minister, Katō Takaaki, opposed accession to the declaration. He considered the alliance with Britain entirely sufficient and believed that a new obligation would needlessly tie Japan’s hands. The matter moved only after his departure from the government in the summer of 1915. A keen supporter of accession was the ambassador in Paris, Kikujirō Ishii, who argued that only in this way would Japan secure a place at the peace negotiating table. On 13 October Ishii took over the foreign ministry, and only six days later Japan acceded to the pact.

Five allies

That same day in the House of Commons the MP Carlyon Bellairs asked the government whether it could lay papers concerning Japan’s further participation in the war and its readiness to send troops against the common enemy. The Under-Secretary of State at the Foreign Office, Robert Cecil, replied that it would not be desirable at present to publish such papers. The news of Japan’s accession to the declaration soon reached the press, however. In its December issue the New York monthly Current History wrote that Britain, France, Russia, Italy and, since the previous month, Japan as well had agreed not to negotiate peace without the consent of all.

On 30 November 1915 Italy acceded to the declaration, having already undertaken to do so in the April Treaty of London. That day representatives of the five powers signed in London a joint declaration repeating the obligation of 1914. Japanese historians count accession to the pact among Ishii’s most important achievements. Japan, although it fought mainly in the Far East and at sea, formally became one of the five principal Allies. According to these historians, this was one of the foundations of its position after the war: in 1919 it sat among the great powers at the Paris Peace Conference, and later received a permanent seat on the Council of the League of Nations.