What are some similarities and differences between the American Civil War and World War II?

The American Civil War and World War II are without a doubt the two most pivotal conflicts in the history of the United States. Let us look at a few similarities and differences between them, beginning with what the two wars had in common. 

Both wars required a massive effort and sacrifice on the part of the American people. Nearly 2.5 million men served in the Union Army during the Civil War, amounting to over 10 percent of the overall population. About 16.5 million men served during World War II, a similar proportion to the overall population. Casualties were horrific in both conflicts. While the Civil War had a higher overall death toll (especially when one includes Confederate casualties) over 400,000 men died in battle or of other causes during World War II. Both wars had a strong ideological aspect. The Civil War began as a war to reunite the Union, but by its end had become a fight to end slavery. World War II was always a war against the forces of fascism and militarism, one which was, at its heart, about the survival of democracy. 

Many of the differences are fairly obvious. The Civil War was an internal struggle, fought on American soil, while World War II was fought overseas. All sides made war on civilian populations in World War II. More civilians than combatants perished in the war, a fact with no parallel in the American Civil War. Another difference was that the emergence of new technologies meant that tactics and strategy had changed considerably between the two wars. The airplane, in particular, completely changed the face of war in World War II.