World War I: Germany declares war on Romania.

Kingdom of Romania

Kingdom in Europe between 1881 and 1947

The Kingdom of Romania was a constitutional monarchy that existed from 25 March [O.S. 13 March] 1881 with the crowning of prince Karl of Hohenzollern-Sigmaringen as King Carol I, until 1947 with the abdication of King Michael I and the Romanian parliament's proclamation of the…