how and when did the dukes of brandenburg become kings of prussia
List of rulers of Brandenburg The early rulers came from several different dynasties, but from 1415 Brandenburg and its successor states were ruled by the House of Hohenzollern for over 500 years. From 1618 onward, Brandenburg was ruled in personal union with the Duchy of Prussia. The Hohenzollerns raised Prussia to a kingdom as the Kingdom of Prussia in 1701, and from then on Brandenburg was de facto treated as part of the kingdom even though it was legally still part of the Holy Roman Empire. The titles of Margrave of Brandenburg and Elector of Brandenburg were abolished along with the Holy Roman Empire in 1806, and Brandenburg was formally integrated into Prussia. Despite this, the Prussian kings still included the title "Margrave of Brandenburg" in their royal style. From 1871 to 1918 the Hohenzollerns were also German Emperors.
William I, German Emperor William I,[2] or in German Wilhelm I.[3] (full name: William Frederick Louis of Hohenzollern, German: Wilhelm Friedrich Ludwig von Hohenzollern, 22 March 1797 â€“ 9 March 1888), of the House of Hohenzollern was King of Prussia from 2 January 1861 and the first German Emperor from 18 January 1871 to his death, the first Head of State of a united Germany. Under the leadership of William and his Minister President Otto von Bismarck, Prussia achieved the unification of Germany and the establishment of the German Empire. Despite his long support of Bismarck as Minister President, William held strong reservations about some of Bismarck's more reactionary policies, including his anti-Catholicism and tough handling of subordinates. In contrast to the domineering Bismarck, William was described as polite, gentlemanly and, while a staunch conservative, more open to certain classical liberal ideas than his grandson Wilhelm II.