Democracy in America, Volume 3 by Alexis de Tocqueville

Any army is in danger of being conquered at the outset of a campaign, after a long peace; any army which has long been engaged in warfare has strong chances of victory: this truth is peculiarly applicable to democratic armies. In aristocracies the military profession, being a privileged career, is held in honor even in time of peace. Men of great talents, great attainments, and great ambition embrace it; the army is in all respects on a level with the nation, and frequently above it. We have seen, on the contrary, that amongst a democratic people the choicer minds of the nation are gradually drawn away from the military profession, to seek by other paths, distinction, power, and especially wealth. After a long peace-and in democratic ages the periods of peace are long-the army is always inferior to the country itself. In this state it is called into active service; and until war has altered it, there is danger for the country as well as for the army.

I have shown that in democratic armies, and in time of peace, the rule of seniority is the supreme and inflexible law of advancement. This is not only a consequence, as I have before observed, of the constitution of these armies, but of the constitution of the people, and it will always occur. Again, as amongst these nations the officer derives his position in the country solely from his position in the army, and as he draws all the distinction and the competency he enjoys from the same source, he does not retire from his profession, or is not super-annuated, till towards the extreme close of life. The consequence of these two causes is, that when a democratic people goes to war after a long interval of peace all the leading officers of the army are old men. I speak not only of the generals, but of the non-commissioned officers, who have most of them been stationary, or have only advanced step by step.