17. In retreats, taking precautionary measures for preserving order; posting fresh troops to support and relieve the rear-guard; causing intelligent officers to examine and select positions where the rear-guard may advantageously halt, engage the enemy, check his pursuit, and thus gain time; making provision in advance for the movement of trains, that nothing shall be left behind, and that they shall proceed in the most perfect order, taking all proper precautions to insure safety. 18. In cantonments, assigning positions to the different corps; indicating to each principal division of the army a place of assembly in case of alarm; taking measures to see that all orders, instructions, and regulations are implicitly observed. An examination of this long list--which might easily be made much longer by entering into greater detail--will lead every reader to remark that these are the duties rather of the general-in-chief than of staff officers. This truth I announced some time ago; and it is for the very purpose of permitting the general-in-chief to give his whole attention to the supreme direction of the operations that he ought to be provided with staff officers competent to relieve him of details of execution. Their functions are therefore necessarily very intimately connected; and woe to an army where these authorities cease to act in concert! This want of harmony is often seen,--first, because generals are men and have faults, and secondly, because in every army there are found individual interests and pretensions, producing rivalry of the chiefs of staff and hindering them in performing their duties.[34] It is not to be expected that this treatise shall contain rules for the guidance of staff officers in all the details of their multifarious duties; for, in the first place, every different nation has staff officers with different names and rounds of duties,--so that I should be obliged to write new rules for each army; in the second place, these details are fully entered into in special books pertaining to these subjects. I will, therefore, content myself with enlarging a little upon some of the first articles enumerated above:-- 1. The measures to be taken by the staff officers for preparing the army to enter upon active operations in the field include all those which are likely to facilitate the success of the first plan of operations. They should, as a matter of course, make sure, by frequent inspections, that the _matériel_ of all the arms of the service is in good order: horses, carriages, caissons, teams, harness, shoes, &c. should be carefully examined and any deficiencies supplied. Bridge-trains, engineer-tool trains, _matériel_ of artillery, siege-trains if they are to move, ambulances,--in a word, every thing which conies under the head of _matériel_,--should be carefully examined and placed in good order.