I was not under the impression that he was actively fighting during the Great War (WWI), he would have been 78 years old when it ended, so I knew that he would have served in the capacity of his specific expertise and vast prior military experience. It shows that he was still in the service during the Spanish - American War (1898), do you know if he had an active part in that War as well as the Filipino - American War which took place just after it (1899 - 1902)?. Just curious....
I would imagine that nearly all of the Civil War veterans who were still living during the Great War (WWI), would have felt quite dated and out of their element regarding war tactics and strategy in comparing how they fought the Civil War and how the Great War was being fought with all of the "firsts" of war appearing for the first time in history, regarding some of the things that I mentioned in post #12 in this OP. I believe that their generation had to have seen the most change in their lifetimes coming from a time of simplicity and modest technology to the turn of the 20th Century where man took his first flight, electricity replacing oil lamps in large population centers, the industrial revolution, automobiles being massed produced and war being waged on a world stage for the first time with all of the inhumanity that was introduced such as chemical weapons and poison gas. The next generation to have witnessed such change were their children and grandchildren who were the ones who fought in WWII with the atomic bomb, the invent of the Jet engine, the space race, man orbiting the earth for the first time, man landing on the moon, aircraft breaking the sound barrier, the invent of global commercial air travel, cars reaching the speed of 200 miles per hour, television being placed in the home, computers being introduced and the internet changing life dramatically allowing immediate access of information to be obtained at the click of a mouse.