OK, I was going to let this one lay silent, but things need to be said. In the 'Expedtion' of question, according to what I researched, there were 11 Regiments, some 11,000-14,000 soldiers that were involved in the action. Not including the field artillery, the Signal Corps, and the Aero Squadron. Now maybe not all the regiments, companies, platoons, etc. carried two 1911's, but it could be possible that some did, as reported by the 'Uncle'. I know if I personally were to be involved in such a military expedition, I would want as much firepower as possible, regulations be dammed and if I could buy and get another, would carry two. I doubt if whatever the number of photographers that went, they didn't get photo's of every unit, no matter the troop size(as Mule Ear M stated). As far as the 1903's being slung over the back with a sling or in a scabbard, somewhere in a book or magazine, I saw a picture that was described as US Army Troopers in Mexico during the 'Expedition' and they had their 1903's slung over their backs, via a sling, while on horseback. Tried to find it, but not successfull. Not saying scabbards werenot the norm.
Now if the Uncle told his 'wide-eyed nephew' they did it as he reported, I have no problem with it. My Dad spent a year before Pearl Harbour in the US CoastGuard (was in combat with German U-boats in the N Atlantic before war was declared-dropping depth charges on the subs), spent two years in the North Atlantic (convoy duty), 6 months in the Med, and 1 1/2 yrs in the S. Pacific (14 amphib landings).He has had to correct certain writings that were suppose to be the 'true' account of what happened in events he participated in. The writers who were reporting on events he was involved in and witnessed, wrote about them 40-60 yrs after the fact, but they weren't there, but relying on just the facts as they gathered them. Dad many times said "That's not how it really happened" and then would relate the facts. Dad just passed away last Oct 7th at 96, still a Proud Coast Guardsman!
I spent 21 yrs as a Police Officer and there are a number of photgraphs of me in uniform, all showing a 4" Colt Trooper 357 Mag on my right side. Unless a person was one I served with or one I told, no one is aware that I most of the time (night duty) carried two revolvers. I had a S&W Mod 60 tucked in a holster behind my Sam Browne (behind my bullet loops), sight unseen. Now if a person was unaware of this and was told that I carrried two weapons and they had pictures or seen such ones of me, they may declare that the photographic evidence doesn't show this. Since they didn't serve with me or were never told, how would they know?
Finally, St George, I don't desire or intend to get into one of the "post wars' that I see from time to time on this Forum, but I do appreciate your knowledge you've gained from research, studying, and even being involved with the many aspects of firearms and histroy, but even the best gained knowledge doesn't always have all the answers. If the 'wide-eyed nephew' says his uncle related the facts as reported by Jubal Starbuck, then I have no doubt that it could have gone down as reported. I've known Jubal since we was wee lads and he is a pretty good measure of people (ie-can seperate the BS'ers from the truthfull). As far as the 'wide-eyed' nephew, well, I've never met him, but have heard alot of positive's about him. Oh yeh, the 'wide-eyed' nephew is desended from and related to Cival War, WW1 and WW2 vets, besides the Uncle who 'could tell a helluva tale' that was on the Expedition. Another footnote-that 'wide-eyed' nephew is he himself a Marine combat vet of Korea (five times wounded), a Marine combat vet of Viet Nam, and retired a Major in the United States Marines. The 'wide-eyed' nephew then went on to serve as a Police Officer in a major city California Police Department and the California Highway Patrol for many years untill retirement age. A believeable man from a honored past!