三国干渉
In 1902, Japan formed an alliance with Britain, the terms of which stated that if Japan went to war in the Far East and if a third power entered the fight against Japan, then Britain would come to the aid of the Japanese. This was a check to prevent Germany or France from intervening militarily in any future war with Russia. Japan sought to prevent a repetition of the Triple Intervention that deprived it of Port Arthur. The British reasons for joining the alliance were to check the spread of Russian expansion into the Pacific area, to strengthen Britain's focus on other areas, and to gain a powerful naval ally in the Pacific.