Reinforcing an Assault Hex + Lone Leaders in Assault

[wleonard1]

So if there is an assault hex active, and another stack comes in to join in on a later turn or action can you disobey stacking rules? If troops have fired on a turn as well, and another stack jumps into the assault do they receive the firepower from the ones that have already fired? Do defenders fire a second time again as well?

No, you can't disobey the stacking rules.  You can only bring in reinforcements up to the stacking limit.
If some troops on the attacking side have already fired, they cannot fire again along with the new entrants.
But all of the defenders can fire again.

Yes, it sounds terribly unfair to the attacking side.  But there are some situations where it might be useful to split up your attack - for example, if you are trying for a double demoralization.