Interestingly enough, despite the idea that the draft subjugates or enslaves the people to the state (involuntary servitude), the draft has historically been the great unifier of states, making people of all classes and regions part of the same citizenship (granted, this is more towards establishing a cohesive nation-state, but democracy and nationalism went together during the first half of the 19th century when this phenomena began). A voluntary force doesn't do that because some regions or classes are invariably more attracted to armed service than others.
Of course, a draft has to be fair and impartial. The American Civil War had a draft that allowed the rich to buy a replacement and Vietnam had some problems with people entering into positions that were either exempt from the draft or wouldn't serve overseas.
Please don't overlook the biggest issue- that it applies to members of one sex only.
Also,drafts are not about unification of equals. Unification of equals is voluntary and symbiotic. Drafts are about saying "join with us or be punished".
The simple truth is that we're dealing with an attitude that says young male humans have some sort of natural obligation to pick up weapons, fight, suffer and die on behalf of other people and the goals of the powerful, who, lest we forget, always have and always do treat the majority of young men as a disposable resource. We are also dealing with an attitude that encourages the idea that young men should fight to preserve the very nations which enforce such things upon them and their future sons. This thinking is responsble for not only the suffering of millions of young men and boys throughout history but for the near-continuous warfare among human communities for millennia. Seeing your nation's young men and boys as a resource for your wars leads naturally into war. Defining young men in terms of utilities of war leads naturally into atrocities including full-on slaughter of any and all adolescent and young adult males in regions consumed by war (a common occurrance). It leads to tension and conflict between competing nations, whose citizens are trained to see their neighbours as threats. Your young men are told they have to enlist and defend against the threat of
their young men, who are all lined up with weapons. Your sons become nothing more than shields and sandbags between nations whose governments are perfectly willing to sacrifice any of them for their own goals, and whose petty territorial or ideological disputes threaten to drag these nations into destructive conflict. If you see your sons in terms of "oh look, soldiers here", you will always have war. You must learn to separate the idea of a young male from that of a potential solidier. This is something no nation, or organizations like the UN, have yet been able to do, as it goes against millennia of human social conditioning. But it must be done. You must learn to look at me and see a
person, unique and precious, not a piece of war material.
As for unifying a state, military service unifies it
against another state. That's what armies are for. Peacekeeping law-enforcement agencies or disaster-response agencies are something different. An army stands
opposed to someone else. If America has a draft, you signal to the world, "we are a warlike nation. Our sons, in our own eyes, are nothing but a resource for war". The nations you have conflicts with will not disagree with you. They will say "America's young men are a resource for war", and they will convince all their people to see their own young men in similar terms to stand opposed to the threat America poses. It is high time for you to step back from war, to signify that your sons are not a resource to be used and sacrificed.
Drafts will not bring peace, they will not bring security, they only ever fuel conflicts, and place ALL young men and boys in the position of being "legitimate targets" for the enemy (be in no doubt, they will be automatically treated as such by most nations), and playthings for their own nation.
