Frederick II became king of Prussia in 1740, inheriting the army and administrative resources developed by his father. He quickly invaded Silesia, taking advantage of the succession crisis in the Habsburg monarchy. The ensuing Silesian Wars made possession of that wealthy province a central issue in European politics. His willingness to initiate war contrasts with the peaceful reforming image sometimes associated with enlightened monarchy. Military success increased Prussia's resources and standing but imposed heavy costs.

In the Seven Years' War from 1756 to 1763, Frederick fought a coalition including Austria, France, and Russia. Victories such as Rossbach and Leuthen displayed tactical skill, while defeats and losses repeatedly threatened the monarchy's survival. The change in Russian policy after the accession of Peter III helped relieve the pressure. The peace settlement confirmed Prussian possession of Silesia and established the kingdom as a major European power. Its survival depended on diplomatic developments and accumulated state resources as well as Frederick's command.

Frederick promoted agricultural recovery, settlement, drainage projects, manufacturing, and a more effective bureaucracy. He supported legal reform and a measure of religious toleration, while social hierarchy, military discipline, and serfdom remained fundamental features of his state. His French writings, flute playing, and patronage at Sanssouci associated him with Enlightenment culture. Relations with Voltaire illustrated both intellectual ambition and the difficulties of linking a philosopher's independence with royal favor.

Prussia participated in the first partition of Poland in 1772, gaining territory that connected important parts of the monarchy. The acquisition involved the dismemberment of a neighboring state rather than a voluntary union. Frederick later confronted Austria in the War of the Bavarian Succession and continued shaping alliances to prevent rival expansion. He died in 1786. His career combined military conquest, state administration, and literary and artistic activity in a highly personal form of rule. The label enlightened absolutist describes selected reforms and cultural interests, not democratic government or equal citizenship. Prussia's increased strength rested on both practical reconstruction and coercive institutions, and his wars left consequences extending well beyond the borders and lifetime of his monarchy.