Promotion with a fork

Draw White to move · Endgame principles · Difficulty about Elo 1500

The plan

The sister lesson to Saavedra, and it shows the same lesson from the other side: underpromotion is not a curiosity but sometimes the only move there is. White is a rook down and has only a pawn on the seventh rank. Promoting to a queen or a rook loses — the black rook checks from behind, and the new piece falls or it is mate. Only promoting to a KNIGHT holds, and that is because it comes with CHECK: Black has to respond instead of striking first. After that the work is not yet done, because the fresh knight stands alone in the corner of the board and is hunted by the black king. Here too there is exactly one move that holds — the knight has to head into the board, not cling to the edge. From then on it always escapes: a rook alone cannot catch a knight as long as it has room.

Rule of thumb: before you automatically promote to a queen, check whether a knight gives CHECK — a tempo is worth more than the strongest piece. Compare 'Saavedra — the queen is too strong'.

Why this level: Underpromotion with a fork — the idea has to be at hand

The solution, move by move

1. 1. c8=N+ The ONLY move that holds, out of twelve. Queen and rook lose, the bishop loses, every king move loses — only the knight comes with check and gets White the one tempo that was missing.
   Sideline 1. c8=Q The strongest piece — and the fastest way to lose. It arrives without check, so Black is to move. 1… Rc1+ The check from behind. The white king has to move away, and it cannot take the queen with it. 2. Kb4 Rxc8 Queen gone, rook against the bare king: lost.
2. 1… Kc7 The king has to get out of check, and attacks the knight while doing so. All seven moves hold the draw for Black; he can no longer win.
3. 2. Ne7 Again the ONLY move out of twelve. The knight has to head into the board. On a7 or b6 it would stand on the edge, where king and rook together can trap it — on the edge a knight is always in danger.
   Sideline 2. Nd6 Standing in for every knight move to the edge or close to the king: the knight needs distance. 2… Kxd6 Simply captured. Rook against a bare king is mate.
4. 2… Kd8
5. 3. Ng6 From here it is technique: the knight keeps its distance from the black king and always has a square. Several moves hold at each point.
6. 3… Ke8
7. 4. Ne5
8. 4… Kf8
9. 5. Nd7+ With check — that wins the knight another tempo and takes it out of reach.
10. 5… Kg8
11. 6. Nb8
12. 6… Kh8
13. 7. Nd7 The knight shuttles back and forth and cannot be caught. Rook against knight with no pawns is a draw: the game is over, even though more moves follow.
14. 7… Kg8

More in Endgame principles

• Saavedra — the queen is too strong White wins
• When to trade White wins
• The pawn too many White wins
• The saving trade Draw
• The king has to come along White wins
• The bishop only sees half the world White wins