Trapped piece

A trapped piece is a piece with no safe square. It does not have to be attacked yet: the trap is the geometry, and the attack is only the last move. The classic victims are the queen after a pawn grab on b2 or b7, the bishop that took on a2 and cannot get back out, and the knight on the rim with every retreat covered by a pawn.

What makes it work is counting escape squares, not attackers. A queen on a crowded board has three or four squares; its own pawns take some of them, enemy pawns and minor pieces cover the rest. When one move covers the last free square and attacks the piece at the same time, the piece is lost, to a pawn if you are lucky.

To spot one, look at every enemy piece on the edge of the board or deep in your camp and list its retreats. If the list is short, look for the move that makes it empty: often a quiet pawn move, or a bishop that attacks the piece and, through it, the squares it would retreat to.

At higher level the trap is played when you are the one attacked. Instead of retreating the attacked piece, look for the counter that attacks the opponent's queen on a square where it has nowhere to go. And watch your own: a queen that takes on b2 usually has two squares left, and one move takes both away.