Queen vs pawn

Despite the substantial material imbalance it's not always a win

The material imbalance in a queen versus pawn ending is big enough that one would think it’s always a win. One beauty of endgames study is that it surprises you often: queen vs pawn has a few fascinating exceptions. Sometimes, despite the incredible imbalance, it’s just draw.

The goals of both parties are clear: the weaker side tries to promote the pawn and the stronger side tries to eliminate the pawn and checkmate the opponent. Interesting positions arise when the pawn is on the last but one rank. Let’s start with a winning position:

Here is the winning plan for the stronger side:

  • Keep checking the king until the opponent king is forced to hide behind the pawn (in this specific position d1)
  • Use that gained tempo to get the king closer
  • Repeat until the king reached the pawn
  • Capture the pawn
  • Checkmate the king

And here is a possible sequence:

The critical position is reached with 8 Qc3+ because it forces the black king to d1 (any other legal move would lose the pawn). What makes this ending fascinating is that this sequence does not always work. Let’s examine the cases in which this sequence fails to achieve the goal or, put it differently, let’s see when the ending is just a draw.

Sometimes pieces or even the stronger king are on the way of the forcing checks. Here is a topical example:

This is a dead draw as there are no useful checks for the stronger side. It’s always interesting to see the smallest change in an endgame position dramatically alters the outcome of a game.

The other exception are rook and bishop pawns. In these positions, the sequence fails to gain a tempo because of stalemate tricks the weaker side can employ to ensure the draw. Let’s look at the critical position with the bishop pawn:

Here black can play Ka1! and capturing the pawn would result in stalemate. This effectively prevents white from gaining the necessary tempo to bring the king closer.

The concept is similar with the rook pawn:

In this position, black plays Ka1! hiding behind the pawn and white must move away the queen from the b file otherwise the resulting position would be a stalemate.

While the rook and the bishop pawn can hold a draw, it’s not always true. If the stronger king is close enough, it’s possible to set up a fascinating mating net:

The most important move in the sequence is 4 Kc4!, that’s what allows the checkmate despite the perfect material balance on the board.

So, let’s recap all cases:

  • A queen wins against a center and a knight pawn unless the king (or any other piece for that matter) prevents the stronger side from starting a forcing sequences of checks
  • A queen cannot win against a bishop or a rook pawn unless the king is so close it can help setting up a mating net