Underpromotion
A pawn can become a knight, a rook or a bishop, and sometimes that wins more than a new queen.
The idea
A smaller promotion sometimes wins more than a new queen does.
- The pawn on e7 is one move from the back rank.
- A knight landing on e8 would check the king on g7.
- That same knight would also attack the queen on d6.
In a game: Look for a promotion that checks, forks or dodges a stalemate that a new queen would cause.
How the lesson begins
A pawn that reaches the last rank must become a queen, a rook, a bishop or a knight. Usually a queen is best, because it is the strongest piece. Choosing a rook, a bishop or a knight instead is called underpromotion. You do it when the smaller piece does something a queen cannot.
Here White’s pawn on e7 is about to promote. Black’s king is on g7 and the queen on d6.
Find the move
Find the promotion that gives check and wins the queen in the same move.
A hint
A knight on e8 would reach both d6 and g7.
Show the answer
1. e8=N+
e8=N+ forks the king and the queen. The new knight checks the king from e8 and also attacks the queen on d6. A knight’s check cannot be blocked, so the king must move, and then the knight takes the queen. The tablebase says this is the only move that wins.
In numbers
In the puzzle bank
520 puzzles in GreyChess’s bank practise it. Half of them are rated between 1,321 and 2,269.
The piece that makes the first move of the answer: pawn 76%, queen 9%, rook 7%, king 5%, bishop 3%, in puzzles from the Lichess puzzle database.