Bishop and pawn against knight — the fortress in front of the pawn

Draw Black to move · Fortresses · Difficulty about Elo 1600

The plan

A piece and a pawn down, and yet the position is indestructible: the black king stands directly in front of the pawn, on the queening square, and it has to stay there. The white bishop is dark-squared, the queening square is light — so it can never attack the king and can never drive it off. It can only take away one of the two neighbouring squares, always only ONE, never both at once. So the defender only needs waiting moves, and the knight supplies them. This is exactly its job in this lesson: attack nothing, defend nothing, simply stay in the game and spare the king from having to move. Without it, the very same position would be lost — then the king itself would have to move and vacate the queening corner. The knight only must not let itself be picked off; it always has a safe square as long as it shuttles near the king instead of running off.

Rule of thumb: king on the queening square, piece as tempo-supplier — as long as the king does not HAVE to move, the pawn does not get through.

Why this level: The knight as a pure tempo-supplier

The solution, move by move

1. 1… Nf3 A knight move — and only the four knight moves hold. Both king moves lose at once, because the king then vacates the queening square (first and second sideline). This is the defender's whole task: leave the king standing and wait with the piece.
   Sideline 1… Kf8 The king goes to the side — the most common blunder, because it looks as if one square were like the other. 2. Bb4+ With check, and this is the difference: this square is dark, and a dark-squared bishop reaches it. On the queening square itself the king would never have stood in check. 2… Kg8 3. e7 The pawn runs, because nobody stands in its way any more. 3… Kh7 4. e8=Q Promoted. A single king step out of the queening corner has cost the fortress.
   Sideline 1… Kd8 The step to the other side is just as bad, only without check. 2. Kf7 The white king immediately occupies the square next to the queening square. From there it covers everything the pawn still needs. 2… Kc7 3. e7 Kd7 4. e8=Q+ The pawn gets through. Two moves after the king left its post.
2. 2. Ba5 The bishop takes the left neighbouring square away from the king.
3. 2… Nh4
4. 3. Bb4 And now the right one — but that frees up the left one again. A bishop can never guard both squares at the same time; that is why the black king is never in zugzwang. In this position only two of Black's five moves still hold, and both are knight moves: the knight has to go back near the king, otherwise it gets picked off (third sideline).
5. 3… Nf3 The knight comes back. It attacks nothing and defends nothing — it is only the tempo the king must not give.
   Sideline 3… Nf5 The knight goes forward instead of shuttling near the king. This is the third way to lose this fortress: it is not the king that moves wrongly, it is the tempo-supplier that gets lost. 4. Kxf5 The ONLY winning move out of fourteen — and the simplest of all: the king simply takes the knight. 4… Kd8 The ONLY move Black still has now. And this is exactly the point: without a knight the king HAS to move, and with that the queening corner is open. 5. Kf6 Kc8 6. Kf7 Kc7 7. e7 Kd7 8. e8=Q+ Promoted. The same position as in the main line, just without the knight — and the fortress has already become a lost game.
6. 4. Kf5 The white king looks for another way. It finds none: it cannot get forward because its own pawn is in the way, and the black king does not let it past on either side.
7. 4… Nd4+
8. 5. Kf6
9. 5… Nf3
10. 6. e7 The last try — the pawn goes to the seventh rank. With that it blocks itself for good: the black king stands in front of it, and it cannot be captured, because the white king protects it.
11. 6… Nd4
12. 7. Kg5
13. 7… Nf3+
14. 8. Kf6
15. 8… Nd4 And so it goes on endlessly. The knight shuttles, the king stands, and with an extra piece and an extra pawn White has not a single way forward.

More in Fortresses

• Rook and pawn against the queen — the castled fortress Draw
• Rook against f- and h-pawns — the gap saves Draw
• Rook against doubled pawns — two pawns that are only one Draw
• Opposite-coloured bishops — one square holds both pawns Draw
• Opposite-coloured bishops — the pawn may even promote Draw