The Kingdom of Bulgaria, also referred to as the Tsardom of Bulgaria and the Third Bulgarian Tsardom was a constitutional monarchy, which was established on 5 October (O.S. 22 September) 1908 when the Bulgarian state was raised from a principality to a kingdom. Ferdinand I was crowned a Tsar at the declaration of independence, mainly because of his military plans and for seeking options for unification of all Balkan lands with an ethnic Bulgarian majority (lands that had been seized from Bulgaria and given to the Ottoman Empire in the Treaty of Berlin).