I must say, I really don't understand the concept of carrying a weapon chambered in 9mm for battlefield pickups.
The rationality is based upon the presumption that NATO Forces would be involved in whatever conflict is going on, yet apparently doing so poorly that they're getting wiped out and leaving a decent supply of unexpended ammo behind for civilians to safely scavenge at their convenience, which strikes me as highly unlikely.
However, my rationality is that if there is going to be much ammo available to pick up from fallen combatants, (which isn't for certain) then obviously their weapons will also be available for pickup, so I'd rather start by carrying something that I feel especially confident with than carry something that I'm not simply because I can salvage ammo for it more readily.
Granted, if you're absolutely confident with 9mm Parabellum FMJ, then this won't be a factor, but personally I'm not, so I'd rather start with something I'm more confident with, then transition to whatever I can scrounge up off the battlefield once I've run out of ammo for my sidearm of choice.
Honestly, no disrespect towards the military, but the standard issue 9mm NATO FMJ just doesn't seem like the most effective handgun round out there, and what's more, a lot of soldiers seems to be of the sentiment that the standard issue ammunition isn't of the highest quality either, so to me, the potential availability of salvageable battlefield ammunition wouldn't be a deciding factor in what I carry. Sure, I'd scrounge up any ammo I might find on the battlefield along with any compatible firearms, but it wouldn't be my first choice. Maybe if the military were at least carrying high quality JHP ammunition, then that would be a more convincing reason to carry a 9mm Pistol from the get-go, but they carry FMJ, hot loaded FMJ ammo, but non-expanding FMJ nonetheless. Stuff that zips straight through a target with a wound diameter no greater than the projectile itself, and a rounded tip which parts tissue more than it crushes or tears.
Personally, I would much rather have a firearm of my own choice with an adequate supply of high quality JHP ammo than compromise by carrying a 9mm Pistol which I could just as easily pickup later with whatever hypothetical supply of 9mm NATO I could loot off of fallen soldiers.