1) Go to the F4 screen, click "Details" and click on the Aztec leaderhead. In the box to the right, you'll the the active deals that you've got going, and the turns remaining. Something like "Military Alliance vs Maya (4)." That means that you've got 4 turns remaining in the MA. If no numbers appear, it's run its course and you can cancel without a rep hit. 2) First of all, if there are still turns left in the MA, I'm pretty sure you'll take a rep hit if you make peace with them before the 20 turns are up, especially as the MA was backed with per-turn goods (horses), if I understand you correctly. Consider just riding out the duration of the MA, then going for peace. If there are no more turns left, or if you want to end it and just take the rep hit, enter diplomacy with the Aztecs. Tell them you want to propose a deal. Then, at the bottom of the diplomacy box, you'll see "New" and "Active." Click on "Active," and that will call up any active deals you have going. You can then click on the deal that you want to work with, and take it off the table.