In the territory of the Holy Roman Empire

Legally speaking, Prussia does not belong to the boundary of the holy Roman Empire of Germany, just because the elector of Brandenburg later merged with East Prussia, and the whole kingdom of Prussia became a part of the German Empire. In the early days, Prussia was a wild land. The ancient inhabitants were old Prussians, and the Prussian language used belonged to the Baltic language family, belonging to the same race as Latvians and Lithuanians. The Teutonic Order launched a crusade in Prussia for nearly 200 years. Prussia became the territory of Teutonic Knights, and Germans, Poles, Lithuanians and other European nationalities came to immigrate. The Teutonic Order forced him to convert to Christianity and use German. /kloc-After the 6th century, Prussians assimilated into Germany and other nationalities, and the Prussian language used gradually disappeared.

1466, the Knights were forced to split Prussia into two parts, and West Prussia was merged into the Kingdom of Poland, while East Prussia was still ruled by the Knights, and it wanted to become a vassal state of Poland. 1655 When the First Northern War broke out, Brandenburg, as an ally of Sweden, entered the war for the first time and defeated Poland. From then on, Brandenburg had complete sovereignty over East Prussia and no longer had to submit to the Polish king.