Why is the civil war considered the ''first modern war?

There are several wars worldwide that are called 'the first modern war'. The Civil War in the US was one of these. Innovations in the Civil War included the first ship sunk by a submarine, use of aerial surveillance to guide artillery, mechanized movement of troops, ironclad ships, rifled guns (both naval guns and infantry weapons), trench warfare, repeating rifles, percussive cannon shells, and more. Many of these innovations were also used in the Austria-Prussia War and Franco-Prussian war, which preceded and succeeded the Civil War respectively.