I think Kerry enlisted, didn't he?
The way I heard it (no guarantees here, so don't quote me) Kerry protested his draft into the army, the draft board wasn't going to give him the rich dude free pass, so he joined the naval reserves expecting to get the GWB treatment.
Much to his surprise, he got activated before his hitch was up. Then he did his job in Vietnam (unlike Gore) while looking for a way out. Applied for a purple heart every time he got scratched in action, demanded transfer to stateside staff work after 3 ph's. When he was ready to enter politics before his release date, he told his CO that he objected to the war and wanted to be released on moral grounds.
Did I get that right?
More on topic:
The draft is every bit against the 13th amendment as every gun control law is against the 2nd. It's involuntary servitude under claim of emergency, when any true emergency (like WWII) results in plenty of volunteers. If you can't do something without enslaving your own citizens, it's time to figure out where you went wrong in deciding to do that.
The Constitutional prohibitions against certain gov't acts are PROHIBITIONS, not meaningless suggestions.