Manstein entered the 3rd Infantry Regiment in 1822. In 1841 he was promoted to first lieutenant and he became an adjutant on the staff of the I Army Corps. By 1864 he had been promoted to the rank of Major General () and given command of the 6th Infantry Division, which he led during the Second Schleswig War in the Battle of Dybbøl and at Als. During the Austro-Prussian War he commanded the reserve of the First Army, which he led during the battle of Königgrätz and for which he was awarded the Pour le Mérite.