Combination
Perpetual Check
Also known as: Draw by Perpetual
Perpetual check is the losing side's parachute. A player who is a piece down, or facing a pawn that cannot be stopped, stops trying to win and starts trying not to lose. If a queen can reach two squares from which it checks the enemy king, and the king can only rock between two squares in reply, the checks never run out. The attacker is never given a free move to convert the extra material, and the game ends in a draw by threefold repetition. It is the most common way a completely lost position is rescued, and it is why a game is never over until the checks are counted.
1. … Qg4+ 2. Kh1 Qf3+ 3. Kg1 Qg4+ 4. Kh1 Qf3+ 5. Kg1 Qg4+ 6. Kh1
The Idea
Perpetual check belongs to the defender. A side that is losing — down material, facing an unstoppable passer, or simply outplayed — hunts for a piece, almost always the queen, that can check the enemy king on squares the king can never run away from. If every check forces a reply that walks straight back into another check, the sequence has no end, and a game with no end is a draw.
The draw is scored by threefold repetition: once the same position, with the same side to move and the same available moves, has occurred three times, either player may claim it. The defender is not mating anyone and is not trying to. The defender is refusing to lose. That is why perpetual check is worth half a point to the side that was busted and a bitter disappointment to the side that was winning.
The Line
In the diagram White is a whole rook up and the pawn on a6 is running for a8, so Black cannot wait. The saving move is 1...Qg4+, sliding the queen from d4 along the fourth rank. It is check down the open g-file, and White's own rook on f1 has taken away the f1-flight square, so 2.Kh1 is forced: nothing can capture on g4, and neither the queen on a5 nor anything else can interpose on g3 or g2.
Now 2...Qf3+ checks the king on h1 down the diagonal through g2. Again there is no choice. The pawn on f2 blocks the rook on f1 from ever reaching f3, the queen on a5 can touch neither f3 nor g2, and g2 itself is covered by the black queen, so 3.Kg1 is the only legal move. Then 3...Qg4+ restarts the cycle: 4.Kh1 Qf3+ 5.Kg1 Qg4+ 6.Kh1. The position that first arose after 2.Kh1 has now stood on the board three times, and Black claims the draw.
Finding It In Time
Look for the perpetual the moment you realise you are lost, not three moves later when the queen has been traded off. The ingredients are an exposed enemy king, a checking piece that can reach two squares which feed each other, and no defender able to block or capture. Here the two squares are g4 and f3: from g4 the queen checks along the g-file, from f3 along the diagonal into h1, and the white king can only rock between g1 and h1.
Count the defender's resources before you commit, because every move must really be a check. The interposing squares — g2 and g3 in this position — must be unreachable, and the checking piece must never be capturable. Notice how much of the work White's own pieces do: the rook on f1 seals the king's only flight square, and the pawn on f2 keeps that rook from ever coming to f3. Change one of those details and White breaks out, and the extra rook wins.
Key ideas
- Perpetual check rescues a lost position by forcing an unending series of checks.
- The draw is scored by threefold repetition of the same position with the same side to move.
- Here the queen rocks between g4 and f3 while the white king rocks between g1 and h1.
- Every move in the sequence must be a genuine check, or the defender simply loses.
- White's own rook on f1 and pawn on f2 are what deny the king any escape.