Army Stacking

This might be a very dumb question, but I'm trying to stack my armies and I can't do it. I haven't played the original Civ IV in years, but I thought stacking armies was as simple as double clicking on a type or alt clicking. None of that is working.

Can anyone tell me how to properly stack my units? It's frustrating moving 10+ guys one at a time. Thank you.

Are those units by any chance hidden nationality? You can't stack those because it was causing endless loops. In other cases I have no problem with alt + clicking, ctrl + clicking or shift + clicking.

Ayup. Hidden nationality. Told you it was a stupid question! I figured it out right after posting this, naturally.

Thank you, Snarko.