The High Middle Ages was the formative period in the history of the modern Western state. Kings in France, England, and Spain consolidated their power, and set up lasting governing institutions. New kingdoms such as Hungary and Poland, after their conversion to Christianity, became Central European powers. The Magyars settled Hungary around 900 under King Árpád (d. c. 907) after a series of invasions in the 9th century. The papacy, long attached to an ideology of independence from secular kings, first asserted its claim to temporal authority over the entire Christian world; the Papal Monarchy reached its apogee in the early 13th century under the pontificate of Innocent III (pope 1198–1216). Northern Crusades and the advance of Christian kingdoms and military orders into previously pagan regions in the Baltic and Finnic north-east brought the forced assimilation of numerous native peoples into European culture.

Along with Poland, what Central European kingdom was formed during the High Middle Ages?