Undeclared War

At a certain stage of civilization, a species is vulnerable to certain types of attacks on their home planet. Earth and mankind have, or are entering that stage. The species that finds Earth first may have ulterior motives to keep their contact secret. And I’m not talking about the usual reasons.
In chess different pieces have different values. Even the lowest pawn, skillfully used can cause the opponent to react in certain ways. I’ve always considered the reaction I get when I move a piece, to determine its value at that particular time.
This very short Science Fiction story could demonstrate where a pawn gains the value of a queen, when skillfully utilized.