If you need to talk to your alliance, request help, information or to leave a comment to one of your alliance without your enemy being able to read it, you need to use the broadcast button

Don't post abuse or unnecessary comments because you may push off a vital message for someone

Some players broadcast a list of their alliance members for you to add

You can request a broadcast of your alliance code to other member's alliances, usually in exchange for a broadcast of their alliance code to your alliance