King of Prussia from 1797 till 1840; incited by the queen and the commons he abandoned his position of neutrality towards Napoleon and declared war in 1806; defeat followed at Jena and in other battles, and by the treaty of Tilsit (1807) Prussia was deprived of half her possessions; under the able administration of Stein the country began to recover itself, and a war for freedom succeeded in breaking the power of France at the victory of Leipzig (1813), and at the treaty of Vienna (1815) her lost territory was restored; his remaining years were spent in consolidating and developing his dominions, but his policy was sometimes reactionary in its effects (1770-1840).