Thanks largely in part to Frederick the Great of Prussia, his father, and the events of the Napoleanic Wars. Prussian military was largely grown from the time it was in, we see Frederick face the combined might of Austria, France and Russia in the Seven Years War, and Austria in the previous Silesian Wars. His reforms to the Prussian military formations, discipline and General Staff largely gave them to best army in Europe. Only to lose his best officers, and his advantage militarily, to the aforementioned Seven Years War. Their defeats in the Napoleanic Wars showed them their days of yore were past, and once again, they reformed for the needs at hand, and once again became a preeminent power. But it was through reforms to combat the present threats that we see Prussia rise as a dominant power until the Prusso-Austrian War and the final Franco-Prussian War.