Cyropaedia

Cyaxares, however, remained behind with one third of the Medes, so as not to leave the home country unprotected, while Cyrus, with the cavalry at the head of the line, marched as rapidly as possible; but he never failed to send patrols ahead, and scouts[*](The order of march) up to the heights commanding the widest view before them. After these he arranged the baggage train, and where the country was flat he arranged many lines of wagons and pack-animals abreast; the phalanx followed next, and if any part of the baggage train lagged behind, such of the officers as happened to be at hand took care that they and their men should not be retarded in their advance.