Answer: William Mckinley was the last president to have been a Civil War Veteran.
Explanation: He was elected President in 1896, but was assassinated in 1901 by a man named Leon Czolgosz.
The reliance could be seen on how we acquire our military draft.
For example, countries such as Russia and south Korea implemented a mandatory military services for all adult men. (they're require to served at the military for around 1-2 years).
United states on the other hand, does not implement such mandatory military draft. All of our forces were acquired through voluntary methods without government force.
Since the nature of war has changed, voluntary method is more than enough since war that conducted on modern time would most likely relied on mass destruction weapons or advanced vehicles.
the Emancipation Proclamation officially took effect, the ideals of the Proclamation had been carefully contemplated by President Lincoln many months before.
Many new machines like the cotton engine. It improved men's clothing and provided new weapons. (Industrial Revolution)