Democracy in America, Volume 3 by Alexis de Tocqueville

It is a part of the essence of a democratic army to be very numerous in proportion to the people to which it belongs, as I shall hereafter show. On the other hand, men living in democratic times seldom choose a military life. Democratic nations are therefore soon led to give up the system of voluntary recruiting for that of compulsory enlistment. The necessity of their social condition compels them to resort to the latter means, and it may easily be foreseen that they will all eventually adopt it. When military service is compulsory, the burden is indiscriminately and equally borne by the whole community. This is another necessary consequence of the social condition of these nations, and of their notions. The government may do almost whatever it pleases, provided it appeals to the whole community at once: it is the unequal distribution of the weight, not the weight itself, which commonly occasions resistance.

But as military service is common to all the citizens, the evident consequence is that each of them remains but for a few years on active duty. Thus it is in the nature of things that the soldier in democracies only passes through the army, whilst among most aristocratic nations the military profession is one which the soldier adopts, or which is imposed upon him, for life.