The answer as it is to most military questions is "Logistics"
Every military leader in history has not wanted to abandon land, but there are always limits to what you can control. What MILGOV can do in an area is limited by how many resources and how relatively little chaos there is in that area.
Maybe one can look at the Causalities by state that Chico drew up. (Ill add a link when i find it)
http://forum.juhlin.com/showthread.php?t=906 post 4
Perhaps if a state has 38% remaining prewar population you could say there was a 19% chance a particular base in that state was never abandoned. ( I divided by half but you could adjust accordingly)
edit chico not web