Prussia owed its name to the Borussi/Prussi, a Baltic people related to the Lithuanians. In 1201, the ‘Brethren of the Sword,’ landed in Latvia and founded the bishopric of Riga, but in 1237 amalgamated with the Prussian Knights. In 1231, Hermann Balke and his crusading army crossed the river Vistula, swiftly founding new fortified cities such as Konigsberg (1255). The Pagan Prussian tribes enjoyed seventy years of prosperity from 1309, after systematic subjection of the people ended. Since Konigsberg sat near the Baltic Sea, it was the main trade port out of Prussia. Exports included flax, hemp, timber and grain. Between 1523 and 1721, the Baltic Sea was busy with many early wooden ships exporting their countries resources to Amsterdam and London.
In 1648, Germany was divided into 234 distinct territorial units, 51 free cities and innumerable estates of Imperial Knights. It was kept weak by religious division and dynamic rivalry. Napoléon and his armies largely solved this problem, when they drastically simplified the German map in 1806. In 1756, began the Seven Years' War when King Frederick II of Prussia, pre-emptively invaded Saxony and Bohemia instead of allowing neighbouring countries to continue to conspire against him. Prussia found itself against a coalition of Austria, Russia, France, Saxony and Sweden, with Great Britain and Hanover as its only allies. Prussia struggled to retain its own territory as the Prussian army was decimated whilst Russia's armies had occupied Berlin. In 1762, the death of Russia's Empress Elizabeth brought her nephew Peter to the throne. Peter III was notoriously pro-German; on his accession, he withdrew his troops and ended the war to no Russian advantage.
Ducal Prussia was a dependency of the Kingdom of Poland until 1660, and Royal Prussia remained a part of Poland until 1772.
With the growth of German cultural nationalism in the late eighteenth and early nineteenth centuries, most German-speaking Prussians came to consider themselves to be part of the German nation, often underlining what were seen as the Prussian virtues: perfect organisation, sacrifice and the rule of law. From the late 18th century, the expanded Prussia dominated North Germany; politically, economically and in terms of population size. Prior to the defeat of Napoléon, Germans were already demanding national unity. Some people wanted a Federal Germany including Austria while others wanted a smaller Germany without Austria. The Franco-Prussian war of 1870-1871 preceded the achievement by Prussia’s Prime Minister, Otto von Bismark of unification in 1871.