DECOY, a stratagem to carry off the enemy’s horses in a foraging party, or from the pasture; to execute which, you must be disguised, and mix on horseback in the pasture, or amongst the foragers on that side on which you propose to fly; you must then begin, by firing a few shots, which are to be answered by such of your party as are appointed to drive up the rear, and are posted at the opposite extremity of the pasture, or foraging ground; after which they are to gallop from their different stations towards the side fixed for the flight, shouting and firing all the way: the horses being thus alarmed, and provoked by the example of others, will break loose from the pickets, throw down their riders and the trusses, and setting up a gallop, will naturally direct their course to the same side; insomuch that, if the number of them was ever so great, you might lead them in that manner for several leagues together: when you are got into some road, bordered by a hedge, or ditch, you must stop as gently as possible; and without making any noise; the horses will then suffer themselves to be taken without any opposition. It is called in French _Haraux_; and marshal Saxe is the only author that mentions it. DECOYED, an enemy is said to be decoyed when a small body of troops draws them into action, whilst the main body lies in ambush ready to act with the greatest effect. DECURIO, in Roman military history, a commander of ten men in the army, or chief of a decury. DECURY, ten Roman soldiers ranged under one chief, or leader, called the Decurio. DEEP, troops are told off in ranks of two, or 3 deep, and on some occasions in 4 or more. DEFAULTER. See DESERTER. DEFEAT, the overthrow of an army. DEFECTION. See MUTINY. DEFENCE, in fortification, consists of all sorts of works that cover and defend the opposite posts; as flanks, parapets, casemates, and fausse-brays. It is almost impossible to fix the miner to the face of a bastion, till the defences of the opposite one are ruined; that is, till the parapet of its flank is beaten down, and the cannon, in all parts that can fire upon that face which is attacked, is dismounted. See FORTIFICATION. _Active_ DEFENCE, generally considered, means every species of offensive operation which is resorted to by the besieged, to annoy the besiegers. Such for instance, is the discharge of heavy ordnance from the walls, the emission of shells, and the firing of musquetry. A mass of water may likewise be understood to mean active defence, provided it can be increased according to the exigency of the service, and be suddenly made to overflow the outworks, or entrenchments of the besieging enemy. Mines which are carried beyond the fortifications may likewise be included under this head.