You cannot force somebody to do something.
If you look at it closely, real closely, you will see that Compulsary National Service is un-democratic.
Firstly, ovcourse you can force people to do things. People pay taxes. People obey the law. They do all that for 2 reasons:
1)They know that as part of a democratic country, the citizen has to pitch in and assist the rest of society.
2) If they don't they go to jail.
Conscription is not somthing politicians do for fun. It is an invaluable way of protecting a country. It is no diffrence than paying taxes, and to be honest usually much better for you. You cant expect to enjoy democracy and than when it needs people to defend it just walk away.
"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself"
John Stewart Mill