The last twenty or so years has greatly changed the emphasis on handguns in military service. Before the GWOT, MPs were amongst the few soldiers issued both a sidearm and a long gun for field work. For other branches, sidearms went mostly to officers, medics, senior NCOs, and some enlisted troopers in crew-served positions. Tankers, for instance, each carried a sidearm for self-defense; if they had to abandon the tank, they shared a single M3 Grease Gun, the M240 coax gun and any ammo they could salvage. The tank was their primary weapon.
It seems nowadays everyone carries both a long gun and a pistol, a change influenced by decades of urban warfare and Special Forces' practice. A 'gunfighter culture' has accompanied these changes, one that places much greater emphasis on service pistols in CQB settings than ever before.
But I think this modern emphasis distorts our conversations about fighting handguns in military service. Handguns were meant to be a backup to a primary or crew-served weapon, to get you off the 'X' when things go pear shaped. You might want more than an anemic .32 ACP. But if that's all you have, it'll do in a pinch -- if you're not already out of Schlitz.
If I had been at Normandy in 1944, I wager I would have been less concerned about whether I carried a S&W M&P or the Colt 1911A1, than whether I had enough ammunition for my M1 Garand. And if I had to choose based on the weight I carried, pass me another bandoleer.
Over several decades of military service, I was issued the 1911A1, M9, S&W 36, Sig 226, and the Sig 229. Like everyone, I extolled or groused about them, for the various reasons you might imagine.
But these were always secondary to the M3 Grease-Gun, M16A1, M16A2/M203, Winchester Model 12 trench gun, Remington 870, or M4 carbine that I carried as my primary weapon. (And on one foreign assignment when I was issued only an M9, I managed to acquire a slightly worn AK-47 under-folder for peace of mind.)