Fredrick William's reign of power continued from 1640 to 1688,Fredrick was elector and Duke of Prussia and Brandenburg.
Frederick William was a military commander of wide renown, and his standing army would later become the model for the Prussian Army. He is notable for his joint victory with Swedish forces at the Battle of Warsaw (1656), which, according to Hajo Holborn, marked "the beginning of Prussian military history", but the Swedes turned on him at the behest of King Louis XIV of France and invaded Brandenburg. After marching 250 kilometres in 15 days back to Brandenburg, he caught the Swedes by surprise and managed to defeat them on the field at the Battle of Fehrbellin, destroying the myth of Swedish military invincibility
Fredrick attended Leiden University from 1601 to 1606.