Rule #2: No secret diplomacy
Any form of diplomatic discussion between opponents must be posted in the game chat in English or in a language that all opponents understand. Diplomacy includes, but is not limited to: proposing truces, negotiating alliances, and coordinating assaults. Secret diplomacy can be hard to prove, but if you suspect it you should leave the players in question appropriate ratings. If you feel certain about players engaging in secret diplomacy consider reporting them in the Cheating & Abuse Reports forum by posting a new topic.
My question :
Does this belong to Secret Diplomacy, if 2 players don't write anything in Game Chat and don't attack each other (or just attack each other in unimportant regions), but they attack other players, because these other players formed a Diplomacy or Cooperation??
Example : Player A and B formed a diplomacy agreement (usually truce on borders) and let the others know. Then player C and D stop attacking each other and attack only A and B. We can say C and D work together. But they write nothing in Game Chat. Does this belong to Secret Diplomacy??