I found a few unusual photos that show Civil War veterans with World War I soldiers and sailors in the Library of Congress. It seems likely these are grandfathers and grandsons.
These photos make you think of what a different thing it meant to be a soldier during the Civil War versus in the Great War. Both would be mustered into military service, lived a regimented life, and deployed, but the similarities end there.
A Civil War soldier from Pennsylvania might be deployed to Georgia, 650 miles away; his grandson, also from Pennsylvania, might be deployed to France 2000 miles away. The Civil War soldier might travel via train, horse, or on foot; the World War I soldier would travel via ship, train, truck, or on foot. The Civil War soldier would be unlikely to meet anyone who didn’t speak English; the World War I soldier would be surrounded by people who spoke English, French, German, Spanish, Italian, and many other languages. The Civil War soldier would have a clear idea of how winning or losing the war would directly impact his life; the World War 1 soldier would not.
The average Civil War soldier was 26 years old, weighed 143 pounds and stood 5’8″. (Library of Congress). The average World War 1 soldier is harder to profile. The average age of a U.S. recruit was 19 (justanswer.com). British WWI soldiers were an average of 5’6″ (nakedcapitalism.com), worldwide 5’2″ (warhistoryonline.com)
Most incredible is the discrepancy in terms of how deadly the war was for a soldier. Despite the new deadly horrors, such as mustard gas and machine guns, that soldiers in the Great War faced, the Civil War casualties dwarfed American casualties in World War I. The casualties from the Civil War were approximately 620,000. U.S. casualties in World War 1 was approximately 116,500.
On one side there is the old world, on the other is the modern world. Seeing them side-by-side show us the torch has passed.
“The Moving Finger writes; and, having writ,
Moves on: nor all thy Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it.”
―

Civil War Veteran Benoni Briggs of G.A.R. Reno post no. 9 with a World War I soldier

Civil War vet in Pennsylvania and World War I soldier

Civil War vet and World War I doughboy

Civil War vet and World War I Sailor