Ok what about the USAF. . . .I'm not 100% certain, but I'd bet windows has a lion share.
You lose.
Most of the Air Force sites I found are using LINUX. The US Air Force Academy was using Solaris but this month switched the OS to LINUX while retaining the Sun server software.
However, the Air Force Reserve web site, www.afreserve.com, and the Air Force Research Lab web site, www.afrl.af.mil, runs on Windows. I hope that pleases you.
BTW: A public facing website really doesn't have a lot of secure data.
However, the military web sites ARE prominent, attractive targets for crackers from the lunatic left who regularly defaced them when they were running less secure software or OSes.
Wow, so you're saying you know what the AF runs internally? Also what do they run on their desktops. BTW: I'll give you a hint...it's not Linux nor Mac.
Finally, what is the AF running on their internal websites for collaboration? Hint: it's not Mac.