As early as 1792, before he had ever seen a battle, he had published a _Soldier's Pocket-book_, in which the principles and details of field service were explained and illustrated by examples from then recent wars. The experiences of his first campaigns in 1793 and 1794 led him during his last years in the Hanoverian service to draw up a series of memoirs in which military education occupies a prominent place, and when in 1801 he joined the Prussian service, one of his first appointments was that of lecturer to the classes of young officers which had been instituted by Frederick the Great and still continued to be held. Scharnhorst rearranged and extended the courses of instruction, and himself as "Director of the Academy" taught to the higher class the important subjects of tactics and strategy. The lectures which he gave between 1801 and 1805 have been preserved in a fragmentary state, and show that he was the first to concentrate the attention of his pupils on the conduct of the operations of war, instead of merely busying them with the details of the several technical arts and sciences which subserve that end. The regulations for the Academy which he drafted in 1805 contain the outlines of the system which in a more developed form is still characteristic of the highest Prussian military education. Scharnhorst's best pupil at this time was Carl von Clausewitz, who in after years attributed to these early lessons the intellectual impulse which produced his masterly essays, and the historical method in which all his theory has its roots. Lectures and classes were abruptly ended by the mobilization of 1805, which was followed in 1806 by the great catastrophe. The War School of 1810 aimed at the higher training of selected officers whose ability gave promise of a career in the superior ranks. It was distinct from the lower schools intended to give a professional training to young men preparing to become officers, and was closely connected with the general staff, in which Scharnhorst, at this time its chief, paid great attention to the instruction of the younger members. One of the first professors appointed was Clausewitz. The wars of liberation practically dissolved the War School, which, however, after the peace of 1815 was re-established without substantial modification, though it was placed in the department, not of the chief of the staff, but of the inspector-general of military education. During the subsequent long period of peace, the Academy had the services of many distinguished men. From 1818 to 1830 Clausewitz was its director. The great geographer Karl Ritter was from 1820 to 1859 one of its professors. In 1859 the title of War Academy was definitely adopted, and in 1872 the institution was again placed under the superintendence of the chief of the general staff.