Once you have talked with another alliance and have decided to go to battle one side will issue the challenge. A challenge can only be issued and accepted by the alliance Leader or Officers.


The foolproof way is this:


Look up a players stats of an alliance member:









Then click on their alliance name, and that will get you to their alliance page:





On the left side of their alliance profile will be a button for "Challenge"






This will take you to a game creation page:
While some people prefer "starts when full" that can be annoying if you are waiting for one player who is not online, or in a different time zone. A better approach is to negotiate with your opposing alliance on a start time and have the game start "immediately" Please note that the game will be running even without being accepted by the other team, so if you accept an old challenge that was "starts now" you may find that the AI have been playing for you, wasting your resources, etc.


A common negotiated point is a Peace Period. Everyone has their own preference. After much discussion the Alliance World Cup rules were standardized at 2 days for AI peace and 3 days Human Player peace.




Once the game is created the challenged alliance needs to accept it. This will be located in the Alliance Games tab of the Alliance tab.