I disagree.

There are currently 1.5 million active troops. If you account for those votes along with the votes of their parents, grandparents, siblings... perhaps even aunts, uncles, etc.... that's enough to make a very strong impact. Especially in regional elections, but even National (I think an 80% or so anti-war stance for military families in Ohio and Florida would have made a pretty significant difference)
Military families could be a powerful voting bloc, trouble is, as Austin put it, most Military officers are Pro-Republican because they build much more lavish officers clubs and always find the cash for the latest military toy.