Perpetual check
A perpetual check is a run of checks that the defending king cannot sidestep, so the same positions recur and the game is drawn by repetition, rescuing the side that was losing.
Perpetual check is a rescue. When you are behind in material or facing a lost position, you can still draw if your queen, or sometimes a rook, can keep giving check and the enemy king has no way to hide. The checking piece shuttles between two squares, the king steps back and forth, and because the same positions keep coming back, the game is drawn by repetition.
To spot it, look at the enemy king and count the squares it can use. If the king is on the edge, with few flight squares, and your queen can check from one square and then from a second square after the king moves, you may have a perpetual. Also check that the opponent cannot block a check with a piece, capture the checking queen, or run to a safe area where the checks stop.
To use it, calculate each check and each possible reply, not only the one you hope for. A perpetual that fails by one blocking move can lose the game, because the opponent's extra material then decides. Before you start, confirm that every single check leaves the king only the squares that allow your next check.
To defend against it, the side that is ahead should look for a way to put a piece in the way, give the king more space with a pawn move, or trade the queens. Making an escape square early, before your opponent finds the checks, is usually the cheapest cure.
In the diagram, White is behind in material, but White to move plays Qe8+. The king can only step to h7. Then Qh5+ forces the king back to g8, because every other square is covered or blocked. After that Qe8+ comes again, and White can repeat the checks to draw.
Compare it with Queen endgame. A queen endgame is an ending in which each side still has a queen, usually with a few pawns, where checks, perpetual check and passed pawns tend to decide the result.
A neighboring idea is Stalemate trick. A stalemate trick is a resource for the side that is losing: it forces the stronger side into a position where the weaker side has no legal move and is not in check, so the game is drawn.
Compare it with Counterattack. A counterattack is a reply to a threat that answers it with a threat of your own instead of defending, usually a larger one, so the opponent has to deal with yours first.
Knowing "Perpetual check" helps most once you can spot it in a real game. A first lesson with George Li starts from your own games and finds the tactics you keep missing.
Related terms
A stalemate trick is a resource for the side that is losing: it forces the stronger side into a position where the weaker side has no legal move and is not in check, so the game is drawn.
A double check is a single move that puts the enemy king under attack from two pieces simultaneously, typically one that moved and one it unmasked, so only a king move can answer it.
A quiet move is a move that makes no capture and gives no check, yet creates a decisive threat or removes the opponent's last defense, so it is easy to overlook among more forcing moves.
A queen sacrifice gives up the strongest piece on the board, usually with a check or a capture, to win through a forced checkmate or to gain enough other material to be clearly ahead.
Guides that go further
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