At the beginning of its institution, the _Dépôt de la guerre_ was no more than archives, where were collected, and preserved with order, the memoirs of the generals, their correspondence, the accounts yet imperfect, and the traces of anterior military operations. The numerous resources afforded by this collection alone, the assistance and advantages derived from it on every occasion, when it was necessary to investigate a military system, or determine an important operation, suggested the idea of assembling it under a form and classification more methodical. Greater attention and exactness were exerted in enriching the _Dépôt_ with every thing that might complete the theoretical works and practical elucidations of all the branches of the military art, Marshal DE MAILLEBOIS, who was appointed director of this establishment in 1730, was one of the first authors of the present existing order. The classification at first consisted only in forming registers of the correspondence of the generals, according to date, distinguishing it by _different wars_. It was divided into two parts, the former containing the letters of the generals; and the latter, the minutes or originals of the answers of the king and his ministers. To each volume was added a summary of the contents, and, in regular succession, the journal of the military operations of the year. These volumes, to the number of upwards of two thousand seven hundred, contain documents from the eleventh century to the close of the last American war; but the series is perfect only from the year 1631. This was a valuable mine for a historiographer to explore; and, indeed, it is well known that the _Memoirs of Turenne and of Condé_, the _History of the war of 1741_, and part of the fragments of the _Essay on the Manners and History of Nations_, by Voltaire, were compiled and digested from the original letters and memoirs preserved in the _Dépôt de la guerre_. Geographical engineers did not then exist as a corps. Topography was practised by insulated officers, impelled thereto by the rather superficial study of the mathematics and a taste for drawing; because it was for them a mean of obtaining more advantageous employments in the staffs of the armies: but the want of a central point, the difference of systems and methods, not admitting of directing the operations to one same principle, as well as to one same object, topography, little encouraged, was making but a slow progress, when M. DE CHOISEUIL established, as a particular corps, the officers who had applied themselves to the practice of that science. The _Dépôt_ was charged to direct and assemble the labours of the new corps. This authority doubled the utility of the _Dépôt_: its results had the most powerful influence during the war from 1757 to 1763.