DECANUS, in Roman military history, an officer who presided over ten other officers, and was head of the contubernium, or serjeant of a file of Roman soldiers; hence our _Deacons_. DECHARGEURS, _Fr._ are men appointed to attend the park of artillery, and to assist the non commissioned officers, &c. who are employed on that service. It is the duty of the former to keep a specific account of articles received and consumed, in order to enable the latter to furnish their officers with accurate statements. _To_ DECIMATE, to divide any body of men into as many tenths as the aggregate number will afford, and to make them cast lots for the purpose of being punished. DECIMATION, in Roman military history, a punishment indicted upon such soldiers as quitted their post, or behaved themselves cowardly in the field. The names of all the guilty were put into an urn or helmet, and as many were drawn out as made the tenth part of the whole number: the latter were put to the sword and the others saved. DECIMER, _Fr._ See DECIMATE. DECLARATION _of war_, a public proclamation made to the citizens, or subjects of a state, declaring them to be at war with any foreign power, and forbidding all and every one to aid or assist the common enemy, at their peril. DECLIVITY, as opposed to acclivity, means a gradual inclination, or obliquity reckoned downwards. DECOMPTE, _Fr._ signifies a liquidation, or balance, which from time to time was made in the old French service, between the captain of a company and each private soldier, for monies advanced, or in hand. In the British service every infantry soldier is settled with on the 24th day in each month. The cavalry is paid every second month. In the American army the soldiers are required to be paid every two months at least. DECOUVERTE, _Aller à la découverte_, _Fr._ To patrole. In the old French service, the party ordered to perform this duty, when in a garrison, usually went three miles round the fortifications to pick up stragglers who could not account for themselves, and to secure spies, should any be lurking about. _Aller à la_ DECOUVERTE, when applied to any party that is detached from the army, signifies to reconnoitre the enemy. Cavalry are usually employed upon this duty.