In genuine democracies, compulsory service in the armed forces is
exceptional. Finland is one of the relatively few outliers. Public support for a
strong defense including conscription is high. Our historical experience has
taught us caution in deconstructing military capabilities. But besides latent
threats from the outside, there are more general reasons to hold on to
Social coherence is significantly improved by the knowledge that the great majority of men have to pass through the same ordeal. Conscription is the most egalitarian institution of a democratic state.
Male self-worth and maturity get a boost by the immersion in an organization, which demands substantial personal effort in combination with extreme group solidarity. Boys (and a few girls) are removed from the bosom of the family and accelerate their advance towards responsible manhood.
Physical condition and social skills are enhanced. This is valuable considering the inadequacies of modern town dwellers. You can even learn a new trade during the military service.
The legitimacy of the armed forces is beyond question in a conscription army. Alienation from the society at large is not on the cards and military conspiracies against the lawful order are unthinkable.
The restriction of liberty is onerous but should be bearable if it
extends to all and everybody. On that score girls, too, should be subject to
compulsory service. A sizable reserve of auxiliary nurses and other supporting
personnel comes in handy in any emergency, military or not.
The effectiveness of a conscription army may be questionable in a high-tech environment. This problem can be circumvented by utilizing civil skills and by using professional standing personnel for intensive training. Frequent refresher exercises are also imperative.
The cost could become excessive. This depends on how long you keep and how you treat your soldiers. In Finland compulsory service is between six and twelve months depending on the rank or skills to be attained. Allowances are small and in general the armed forces are held on a tight regime. A professional volunteer army would probably be less cost effective.
What about conscientious objectors? In most countries they are accommodated by performing public services under strict supervision. In Finland the term is one year.