noun
League of the Three Emperors
Historical term for the alliance between Germany, Austria-Hungary, and Russia from 1873 to 1887.
三帝同盟は1873年に結ばれた。
The League of the Three Emperors was formed in 1873.
From 三 (three) + 帝 (emperor) + 同盟 (alliance). A straightforward compound describing the historical alliance.