DUTY, in a military sense, is the exercise of those functions that belong to a soldier; yet with this nice distinction, that duty is counted the mounting guard, &c. where no enemy is directly to be engaged; for when any body of men marches to meet the enemy, this is strictly called _going upon service_. On all duties, whether with or without arms, picquets, or courts martial, the tour of duty begins with the eldest downwards. An officer who is upon duty cannot be ordered for any other before that duty is finished, except he be on the inlying picquet, as then he shall be relieved, and go on the duty ordered. _Military_ DUTIES may be divided into two general classes, under the heads of Brigade and Regimental _duties_. _Brigade duties_, are those which one regiment does in common with another, collectively or by detachments; and of which the brigade major keeps a regular roster. _Regimental Duties_, are those which the several companies of a regiment perform among themselves, and of which the adjutant keeps a regular roster. The following _general regulations_ are to be observed, respecting duties in general. When field or other commissioned officers, are given out at head quarters for one _duty_, they cannot be taken off to be put on any other _duty_. No officer is allowed to exchange his _duty_ with another, after he has been put in orders for it, without leave of the commanding officer of his regiment. Guards, or detachments, which have not marched off from the parade, are not to be reckoned as for a _duty_ done; but, if they should have marched from the parade, it stands for a _duty_ done, though they should be dismissed immediately. If any officer’s tour of _duty_ for the picquet, general court martial, or _duty_ of fatigue, happen when he is on _duty_, he shall not make good such _duty_ when he comes off. No regiment can demand a tour of _duty_, unless it has marched off the place of parade, and beyond the main guard. General courts martial that have assembled, and the members sworn in, shall be reckoned for a _duty_, though they should be dismissed without trying any person. Whenever the picquets are ordered to march to any parade, it is not to be accounted a _duty_, unless they march off that parade. All commands in the regular forces, fall to the eldest officers in the same circumstances, whether of cavalry or infantry, entire, or in parties. In case two commissions, of the same date, interfere, a retrospect is to be had to former commissions, or to lot. Officers, on all duties under arms, are to have their swords drawn, without waiting for any word of command for that purpose. E. EAGLE. _Black_-EAGLE, an order of military knighthood in Prussia, instituted by the elector of Brandenburg, in 1701, on his being crowned king of Prussia. The knights of this order wear an orange colored riband, from which is suspended a black eagle.