Rotating legions

Twelve legions, corresponding to the number of tribes, were enlisted in the king’s service. Each legion comprised a body of twenty-four thousand men, whose term of service was a month in rotation, and who were stationed either at Jerusalem or in any other place where they might be required. There was thus always a force sufficient for the ordinary purposes of state, as well as for resisting sudden attacks or popular tumults; and when extraordinary emergencies demanded a larger force, the whole standing army could easily be called to arms, amounting to two hundred eighty-eight thousand, or to three hundred thousand, including the twelve thousand officers that naturally attended on the twelve princes (1 Ch 27:16–24). Such a military establishment would be burdensome neither to the country nor to the royal treasury; for attendance on this duty being a mark of honor and distinction, the expense of maintenance would be borne probably by the militiaman himself, or furnished out of the common fund of his tribe. Nor would the brief period of actual service produce any derangement of the usual course of affairs; for, on the expiry of the term, every soldier returned to the pursuits and duties of private life during the other eleven months of the year.

Jamieson, R., Fausset, A. R., & Brown, D. (1997). Commentary Critical and Explanatory on the Whole Bible (1 Ch 27:1). Oak Harbor, WA: Logos Research Systems, Inc.