Romanian soldiers in the Austro-Hungarian Army in Military history of Romania A blog by Morar Andrei Posted November 11 The participation of Romania in the WW1 on the side of the Allieds was a disaster for the country .Romania until the death of King Carol I was at the side of Austria and Germany . inclusive with formal alliance. but the King died and with him his policy. In 1916 Romania declared the war to Austria and invaded Transylvania .in the confidence of the support of Russia .and her great victory over the Austrians .the Brussilov Offensive. the offensive not destroyed the Austrians and the Romanians invading were repulsed and obligated to retreat then the Austro Germans invaded and occupied nearly all Romania . except Iasi .and forced an armistice . and a treaty .