war. An agreement between two belligerent powers for the delivery of prisoners or deserters, and also a written challenge to a duel. 2. Cartel ship, is a ship commissioned in time of war, to exchange prisoners, or to carry any proposals between hostile powers; she must carry no cargo, ammunitions, or implements of war, except a single gun for signals. The conduct of ships of this description cannot be too narrowly watched. The service on which they are sent is so highly important to the interests of humanity, that it is peculiarly incumbent on all parties to take care that it should be conducted in such a manner as not to become a subject of jealousy and distrust between the two nations.