Federalist No. 24
In Federalist No. 24, Hamilton further considers the powers necessary to the common defense, and, in particular, the specific objection that proper provision has not been made against the existence of standing armies in time of peace. In Hamilton's view, this objection rests on weak and unsubstantial foundations, and this is easy to show.
In the proposed constitution, the whole power of raising armies was lodged in the LEGISLATURE, not in the EXECUTIVE; that this legislature was to be a popular body, consisting of the representatives of the people periodically elected. Furthermore, restraints upon the discretion of the legislature in respect to military establishments in time of peace, would be improper to be imposed, and if imposed, from the necessities of society, would be unlikely to be observed.
Furthermore, previous to the Revolution, and ever since the peace, there has been a constant necessity for keeping small garrisons on our Western frontier. No person can doubt that these will continue to be indispensable. In addition, If we should not be willing to be exposed, in a naked and defenseless condition, to the insults and encroachments of Britain and Spain, we should find it expedient to increase our frontier garrisons in some ratio to the force by which our Western settlements might be annoyed.
Thus, standing armies will be needed in times of peace, and it will be up to the Legislature to determine how big they need to be.