The issue of packing a full size pistol is one of the most striking things that i have heard from people i know/have met who have been deployed to combat theaters. From stories my uncle has told of himself and guys from his unit stashing their issue 1911’s in foot lockers and stuffing a personally owned detective special or j-frame in a fatigue pocket while in Vietnam to friends who were involved in both Iraq campaigns and Afghanistan ditching the Beretta to carry more rifle ammo. I used to think that a full size combat pistol would be an essential piece of gear for any infantry soldier, but after talking with a number of people about the actual usefulness (or lack thereof) and the issues with finding an effective carry solution among all the other crap a line troop must carry the idea of a fullsize service pistol made less and less sense.
Timothy J. Mullin has an good book on the subject (though dated) titled The 100 Greatest Combat Pistols which touches on the subject and comes to many of the same conclusions that a big pistol rarely makes sense for anyone that has a better option available.
I personally can’t imagine a scenario where anyone other than maybe an MP on a secured base somewhere is actually going to be able to use a pistol as an effective weapon against even a single adversary in a modern military engagement (SOF is a different story).
I don’t pretend to be an expert, or even purport to have any practical experience on the subject, but listening to those who have had experience certainly has changed my thought process.