What year did the Babenbergs aquired the Duchy of Styria ?
Armed conflicts arose especially around the multilingual town of Maribor , until by the 1919 Treaty of St Germain the former duchy was partitioned broadly along ethnic lines , with two thirds of its territory ( then called Upper Styria ) including the ducal capital of Graz remaining with the Federal State of Austria , and the southern third of Lower Styria with Maribor passing to the Kingdom of Yugoslavia , eventually becoming a part of modern Slovenia .