Let me offer some more boring back of the envelope number crunching. I was once a math major, so forgive me.
We've been fighting a war for eight years with an all-volunteer military, which has put a great deal of stress on the Army and Marine Corps, especially. We've done it so far without breaking our ground forces. Right now they've continued to win and are experienced and well trained.
But to keep these experienced and lethal troops in the military where they will make our ground forces the world's best for another generation, we have to reduce the stress of repeated deployments with insufficient rest. We hope to get to 2 years off for every one year deployed.
Can we get to this 2:1 ratio soon? (And the reserves aim for 5:1, or five years off for every one year deployed.) I think we can. And the time it will take to get to this 2:1 ratio for active forces is helped by the fact that in Iraq, where the bulk of our deployed troops are, our troops aren't doing much fighting.
I assume that by the end of next year, we'll have 6 combat brigades/regiments in Iraq (doing training and not called "combat brigades" to finesse the requirement that our combat brigades withdraw).
I'll also assume that we will surge more troops to Afghanistan and have 10 brigades/regiments there by the end of next year, up from the five we have now.
We have 45 active component Army brigades and 9 Marine regimental combat teams, or their equivalents. We also have reserve Army brigades in the Guard and reserve Marine regiments that total another 31, which could provide 5 brigades/regiments per year without too much strain.
If we want 16 brigades in the field, we need 48 brigades total for 2 years off and one year deployed. But that only works if units just appear and disappear. We need to move units and let them overlap with the unit they replace. Multiply this 48 brigades by 1.15 to account for overlaps and transport, and you need 55 brigades to field 16 brigades overseas with 2 years home.
Even accounting for holding a few brigades out of the rotation for South Korea and as a strategic reserve, if we use our reserve brigades we will have enough brigades and regiments to ease the strain of deployment, and fight in Afghanistan while stabilizing Iraq.
Of course, this all assumes we only need to deploy to Iraq and Afghanistan for the next several years.
And I still worry about putting so many troops into landlocked Afghanistan. But that's another worry about different numbers.