Spoilers up through the first episode/chapter of "The Human Division"
So the Colonial Union has been using Earth as a breeding ground for centuries. People from first world countries are recruited when they turn 75 to become soldiers, while people from third world countries of any age are recruited as colonists.
For those who haven't read Old Man's War and ignored the spoiler warning, this works because pretty much the first thing that happens with soldiers is their minds are transfered from their 75 year old bodies to freshly cloned, genetically modified and cybernetically enhanced bodies.
They then serve until the die or hit ten years, at which point they get the option to retire. When and if they use that option they're moved to a new non-genetically engineered but still young body and can become a colonist.
(The question of how exactly the mind transference works and if they mind is really being transfered or if a copy is being made and the "real you" dies immediately thereafter has been raised in the books, though currently seems to be viewed as fundamentally unanswerable.)
Supposedly this system allows the Colonial Union to produce soldiers and new colonists out of proportion to the strength of the other alien races. (Do those races not breed as fast as us? Or do they have home worlds with multi-billion populations as well but are unable to convince those people to either sign up for the military or emigrate?)
Then a diplomatic split is "engineered" between Earth and the Colonial Union, and they lose access to both their supply of soldiers and new colonists. In the first chapter of "The Human Division" a none too bright government functionary asks if that's really a big deal. One of the heads of the military, in the process of explaining to him that yes in fact it is, asks if _he_ wants to sign up for the military given the not too spectacular survival rate?
Which immediately makes me think, "hell yeah!"
At least, nothing has been said in the books about humans effectively being immortal now. It's never mentioned in an aside about how colonist so-and-so is getting around to the point where they'll need a new body.
Which leads to two possible situations. The Colonial Union is desperately in need of bodies and has the ability to regenerate old people who are about to die, but chooses not to. (I do seem to remember something about the process being the exclusive property of the Colonial Marines, but i can't find a reference for it right now.) Or everyone in the Colonial Union is effectively immortal and somehow this HUGE change in the human condition hasn't been brought up.
If it's the first case, one wonders why there haven't been civil wars already given that immortality is an option but apparently isn't being offered.
But even if the Colonial Union has for some reason held back the rejuvenation treatment for military use only, and only chosen to recruit people from Earth, and somehow hasn't been kicked out of power before now because of it, why the hell wouldn't they change their mind now?
I can understand the temptation to sign up for the military if you could do it at 75 and get a new young body in exchange. I don't know exactly what the normal life expectancy is without rejuvenation, but i'd be seriously tempted to do it myself despite the casualty rates. Why wouldn't colonists make the exact same decision when they started getting older? And for the relatively small percentage that survived combat, retired in a fresh new body and got old all over again the temptation would probably be even stronger. You survived it once after all, so why not do it again?
And realistically it would probably be true. It's generally accepted (both in real life and in books) that casualty rates are highest amongst new recruits because of the learning curve. The "second generation" soldiers ought to have a leg up on the competition.
Barring the possibility of just giving rejuvenation to everyone for free on their 75th birthday, this seems like it ought to be a win-win-win situation for everyone involved. The colonists get the chance to become young again, and the Colonial Union gets more soldiers _and_ more colonists. It might not be enough to make up for losing Earth, but it's sure a hell of a lot better than nothing.
Of course on a related note, with supplies from Earth cut off, shouldn't Ghost Brigade production be going into high gear about now just by default? Or did that get project get disbanded at some point and i've forgotten about it?
Cross-posted from G+ here