AThe Union can be joined when a clan leader with more than 20 clan members searches for a union. If you want to create a new union, you can create one on the Federation Creation tab.
Up to 10 clans can join a single union.

AClan unions can be joined only when there are more than 20 clan members. If you lose more than 20 clan members, you will be automatically removed from the union. Same rule applies for Clan Union Representatives as well. One's position will be handed over to the next leader of the highest ranked clan within the Clan Union.

In other cases, you may be removed from the union by the Clan Union Representative.

AClan unions can be joined only when there are more than 20 clan members. If you lose more than 20 clan members, you will be automatically removed from the union. Same rule applies for Clan Union Representatives as well. One's position will be handed over to the next leader of the highest ranked clan within the Clan Union.

In other cases, you may be removed from the union by the Clan Union Representative.