I am not sure what you are asking, the next Civil war (for lack of better words) is not going to be a medieval battle field where we charge at each other with swords or a Vietnam type guerrilla offensive where we have to run up and down a Ho-Chin-Min trail. So how many of what age & shape isn't going to matter as much as you think.
What's going to happen is some kind of spark in one or more of the major cities, maybe it will be a Rodney King or a Crown Heights type of incident, maybe there will be a scorching couple of days in the summer which causes regional blackouts, or maybe another Katrina or other natural disaster.
Whatever the spark, this time once the rioting and looting starts it's not going to stop, and it's going to spread to other cities. Obama is not strong enough to put it down even if he wanted to(See Cloward + Piven).
The Cities will be in flames and "No-Go" zones, while life will initially go on in the country relatively normal. There's plenty of stuff to loot in the cities, there's no reason for them to come out right away, they will kill each other fighting over their resources first.
City people are not self reliant, especially city Liberals, for example ask them why they don't own gun and they will tell you "I don't need one, I'll just call the police" and White city Liberals have been so feminized they will be lambs to the slaughter. They are all going to die waiting for Obama to come save them.
You'll have some squatters camps of refugees in many of the rest areas on the interstates on the outskirts of the cities, but full coordinated attacks on small towns dozens or 100s of miles away, it's not going to happen.