Yes, me and the questions again.  I play mostly on PBW, so I get a turn every two days or so.  I guess I should start a single player game to test these things!   
Question:  If I have a treaty (Not Alliance).  What options in the treay will allow us to fight as one in a Battle?  Do alliances work better for joint combat, when alliances work!?
In a PBW similtaneous game, Can you move and fight together?
Any suggestions you've learned to make the process work smoothly, so allies can work together?