The Anglo-Japanese Alliance (日英同盟, Nichi-Ei Dōmei) was an alliance between the United Kingdom and the Empire of Japan which was effective from 1902 to 1923. The treaty creating the alliance was signed at Lansdowne House in London on 30 January 1902 by British foreign secretary Henry Petty-Fitzmaurice, 5th Marquess of Lansdowne and Japanese diplomat Hayashi Tadasu. After the preceding era of unequal treaties enforced on Asian countries including Japan, the alliance was a military pact concluded on more equal terms between a Western power and non-Western nation. It reflected the success of Meiji era reforms that modernized and industrialized Japan's economy, society and military, which enabled Japan to extract itself from the inferior position it had previously shared with other Asian countries like China, which had been subordinated to Western empires either through formal colonial acquisition or unequal treaties.
One shared motivation for the agreement was that a diplomatic alliance might deter other world powers that might otherwise encroach on British and Japanese imperial interests in Asia. For the British, the alliance marked the end of a period of "splendid isolation" while allowing for greater focus on protecting its rule over India and competing in the Anglo-German naval arms race, as part of a larger strategy to reduce imperial overcommitment and recall the Royal Navy to defend Britain. By contrast, it came at a time of Japan's ascendancy; Japan had not only successfully abrogated the unequal treaties it was previously subject to by the Western powers, but was now a fledging empire in its own right: Japan had imposed its own unequal treaty on Korea in 1876 and now controlled Formosa (Taiwan) as a colony, as Taiwan been ceded by Qing China to Japan in the Treaty of Shimonoseki, after the First Sino-Japanese War. Consequently, Japan was now developing its own imperial sphere of influence, and felt that a conflict with Russia was imminent over rival ambitions in Manchuria and Korea, especially after the Triple Intervention in 1895, in which Russia, France, and Germany coerced Japan into relinquishing its claim on the Liaodong Peninsula. Article 3 of the alliance promised support if either signatory became involved in war with more than one power, and thus deterred France from assisting its ally Russia in the Russo-Japanese War of 1904–1905. Instead, France concluded the Entente Cordiale with Britain and limited its support of Russia to providing loans. Japan also gained international prestige from the alliance and used it as a foundation for their diplomacy for two decades, although the alliance angered the United States and some British dominions, whose opinion of Japan worsened and gradually became hostile.
