After Frederick William IV suffered a stroke, his brother William I became regent (1857) and king (1861–88). He desired to reform the army, which conservatives such as Roon considered to have degraded since 1820 because of liberalism. The king wanted to expand the army—while the populace had risen from 10 million to 18 million since 1820, the annual army recruits had remained 40,000. Although Bonin opposed Roon's desired weakening of the "Landwehr", William I was alarmed by the nationalistic Second Italian War of Independence. Bonin resigned as Minister of War and was replaced with Roon.