Why did men join up to fight in the civil war?

Answer 1

In the North, men joined up in order to save the Union, which was partly patriotism for its own sake and partly an urgent need to rescue the cotton revenues.

In the South, they joined up in response to an emotive appeal to defend their homeland that was under threat of invasion from other Americans now identified as a foreign enemy. For many of this naturally aggressive breed, it was also largely just an excuse for a darn good fight.

There are those who try to reason that the men were fighting for and against slavery. The plain fact is that most Northerners were not abolitionists, and most of the poor white trash of the South cared nothing about slavery either.