Trying to get an estimate on this number, not trying to shit post.

Given modern weaponry compared to that of the time, how many modern soldiers would it take to defeat either the Union or Confederacy?
Not including nuclear weapons or planes.

Would 1000 troops with access to standard small arms plus mortars and howitzers be able to do it?
I figure with how they fought in formation and had to be at a much shorter range, it'd be light shooting fish in a barrel. On the other hand, they'd have a lot more bodies to throw at the 1000 modern troops.