This will be a bit long winded but covers lots of ground from the original post as well as several follow on comments.
As an Active duty soldier and later National Guardsman I carried the M1911A1 pistol as a 95B MP and as an 11B Automatic rifleman (M60 AND pistol). When I transitioned into 11H as a TOW missile gunner I was again issued the M1911A1 as a personal weapon.
Throughout my Army days the pistol was issued with anywhere from one 5 round magazine to three 7 round magazines. In addition the holster was dependent on the duty and what was in supply.
In Korea as a MP I was issued a open top leather rig with safety strap (right or left hand depending on soldier) and one 5 round magazine. New Provost Marshal came on post and we went to right hand flap M1916 holsters for all with three 5 round magazines and later 7 round magazines.
In NYC with the Armed Forces Police we had issued Don Hume basket weave leather gun belts, open top holsters and gear. During a stint in MPI I was issued a Colt Detective special with 6 rounds of ball ammo and we used whatever holster you could get. Mine was a Bianchi paddle with thumb break.
Later National Guard time and the Flap holster was on my side as a M60 gunner and the M7 chest holster was the rig when I was a TOW missile gunner on the ITV 901.
At no point did Army peacetime doctrine allow for the carrying of a M1911 with the chamber loaded UNLESS you were in combat. That is not to say what actually happened on some tours of duty. Those clearing barrels got their holes for a reason you know!
The women MPs and MP Investigators along with Army aviators all had the advantage of a revolver issued to them and usually with full cylinders and a simple trigger pull to make it work. I preferred the revolver to a M1911 for that reason during my army days. Today I understand that the Army and the M9 pistols are often carried with a round chambered and safety on. My Iraq vet co-workers tell me they were issued two 15 round magazines for the Beretta. They put it on safe and chambered a round. The hammer automatically dropped to the DA position and the locked and loaded pistol deposited in the holster.
I have no active or guard time since 1989 and have not been issued the M9 ever. I have however used the Beretta M9 (commercial version), 92FS, 92G and 92D on numerous occasions as a police duty gun and in fact I have a Beretta 92D on my hip as I type this.
Handguns are not routinely needed in the field but there are times when they can be very comforting. I was very happy to have had the ones I did when on duty. I do know that there have been a plethora of after action reports of pistol combat in the sandbox. Several co-workers spent time in Afghanistan, Iraq or both. I was too old and fat to go back in the Guard or else I too would have been there. I have heard the stories but I take more stock in the reports.
Handguns in Iraq for example have been used in greater numbers as primary weapons for house clearing team members and other duties than most any other action. Handguns have absolute advantages in some of those circumstances. Most soldiers I knew wanted one if possible. Except for the tunnel rats in Viet Nam handguns were not so useful in the jungles. Even so they were popular as issued or field pickups.
If I were to go back into military uniform and find myself in Iraq I would opt for a M9 with reliable magazines over the M1911. The modern battlefield has far more scenarios where lots of bullets are better than a few bigger bullets. Handguns are weak pieces of crap compared to combat rifles and a .45 pistol may be slightly better in some ways over a 9mm but it is still a crappy handgun cartridge. Those 9mm europellets have done well in many of those action reports. They excel at penetrating some of the modified armor the bad guys sometimes have as well. Pelvic shots from a 9mm or a .45 seem to be right on the money as far as effectiveness, they both do great. If issued a pistol make mine a Beretta flavored 9.
The bottom line in military circles is a combination of effectiveness and cost. In many cases they are compromised. Even so I think the pistol in military circles is an asset and should be encouraged even though for most it is wasted weight on the belt. If I had my druthers I would select a handgun and cartridge (I favor the .40 GLOCK 22 for that job) as standard for those limited jobs that require a handgun and I would allow individual soldiers to carry personal weapons of their choice in the service caliber. The .40 is a viable compromise that meets the needs of the "lotsabullets" crowd and the "BIG is Better" crowd. The heck with NATO compatibility.
My opinions and worth what you paid for them.