Just started playing. I create a couple of military units, select them and then try to click on "New army", but it's greyed out and I get a message that says "no position to create army". I thought I'd chosen a bad location or something, but I've tried restarting 3-4 times and am getting the same error each time. There must be something *really* dumb that I'm doing wrong, but I can't figure out what. Help, please!

Do you have another army standing on top of your city?

Yes, that was the problem. (Told you it was something really dumb.) Thanks