DEPTH _of formation_. The fundamental order of the infantry in which they should always form and act, and for which all their various operations and movements are calculated, is _three ranks_. The formation in _two ranks_ is regarded as an occasional exception that may be made from it, where an extended and covered front is to be occupied, or where an irregular enemy, who deals only in fire, is to be opposed. The formation in two ranks, and at open files, is calculated only for light troops in the attack and pursuit of a timid enemy, but not for making an impression on an opposite regular line, which vigorously assails, or resists. DEPTH is not only applicable to men drawn up in line, and standing at close, or open files two or three _deep_, but it may likewise signify the relative depth of an army marching towards any given object, in desultory columns. DEPUTY, a term given to persons employed in the civil departments of the army, and subject to superior trusts. DEPUTY _pay-masters_. DEPUTY _muster-masters_. DEPUTY _commissaries_. DEPUTY _judge-advocate_. DEROUTE, _Fr._ The total overthrow of an army, battalion, or of any armed party. See DEFEAT. _To_ DESCEND, signifies to leave any position on an eminence for immediate action. _To_ DESCEND _upon_, to invade. When an enemy from surrounding heights suddenly marches against a fortified place, he is said to descend upon it. The term is also applied to troops debarking from their ships for the purpose of invasion. DESCENT. Hostile invasion of any state or kingdom. DESCENTES, _dans le fossé_, _Fr._ See DESCENTS _into the ditch_. DESCENTS _into the ditch_, are cuts and excavations which are made by means of saps in the counterscarp beneath the covert way. They are covered with thick boards and hurdles, and a certain quantity of earth is thrown upon the top, in order to obviate the bad effects which might arise from shells, &c. When the ditch or fossé is full of water, the _descent_ must be made to its edge, after which the ditch must be filled with strong fascines covered with earth. When the ditch is dry, the saps are carried on to the bottom, and traverses are made in order to secure a lodgment, or to render the approaches of the miner more practicable. When the ditch or fossé which is full of water, has little or no bank, the _descent_ is simply made over it, care being taken to cover its enfilade or range with blinds and chandeliers, or to execute it as much out of that line as possible. DESCENTS, in fortification, are the holes, vaults, and hollow places, made by undermining the ground.