In all actuality, the American Civil War is considered by most historians as the first "Modern" war, where technology outpaced tactics. Rifled weapons and men fighting in straight lines is an example. Thaddeus Lowe and his Balloon Corps observing the confederate lines from above, and steam powered armored gunboats and the first Iron Navy. But if I could go back in time, it would be as a pilot in the first years of the second world war: 1939 to 1942. The weapons (Planes) were technologically advanced and still unlike anything anyone had ever seen over the battlefields, and yet, they were still art.
Following up on others' comments, however; War isn't pretty, it isn't romantic and no one who has experienced combat returns unscathed, physically, mentally or both.
Anyone who says differently has read one too many "Dime Novels"and has never "been there". ( I am certainly no combat expert either, but I knew when to listen to those who WERE there, when they talked).
If you want to watch great movie about guys returning home from WWII, see "The Best Years of Our Lives", with Dana Andrews, Frederick March, Hoagi Carmichal, Theresa Wright, Myrna Loy, Virginia Mayo along with many other great actors. It won the Oscar for Best Picture in 1947.