Following a Celtic (after c. 450 BC) and a Roman (9 AD – c. 430 AD) period, the foundation of Hungary was laid in the late 9th century by the Hungarian ruler Árpád, whose great-grandson Saint Stephen I was crowned with a crown sent from Rome by the pope in 1000. The Kingdom of Hungary lasted for 946 years, and at various points was regarded as one of the cultural centers of the Western world. After about 150 years of partial Ottoman occupation (1541–1699), Hungary was integrated into the Habsburg Monarchy, and later constituted half of the Austro-Hungarian dual monarchy (1867–1918). A great power until the end of World War I, Hungary lost over 70% of its territory, along with one third of its population of Hungarian ethnicity, under the Treaty of Trianon, the terms of which have been consi