Underpromotion in chess is a fascinating and often overlooked aspect of the game. It occurs when a player promotes a pawn to a piece other than a queen, typically a knight, bishop, or rook. This strategic move can be a game-changer, as it can create unexpected threats and opportunities that the opponent may not have anticipated.
Underpromotion is a relatively rare occurrence in chess, as promoting a pawn to a queen is typically the most advantageous move. However, there are situations where promoting to a queen may not be the best option.
Promotion to a knight
Of the three possible underpromotions, promoting to a knight is the most common, as it can create the most unexpected and powerful threats. One of the most famous examples is called the Lasker Trap. It is named after the former World Champion Emanuel Lasker, although it was first noted by an Italian chess master Serafino Dubois. Let’s see how the underpromotion to a knight was crucial to win the game:
Promotion to knight may also be done for defensive reasons. Have a look at the endgame between Gata Kamsky and Étienne Bacrot in 2006. At the position below, White threatens to capture the pawn or checkmate by ♖h1 if the black pawn promotes to a queen, rook, or bishop.
However, after e1♞+!, Black gains an important tempo thanks to the check, and the game is a draw. Well, at least in theory because the actual game was eventually won by White due to Black’s mistakes.
Promotion to a bishop
Promotion to a bishop is quite a rare but still useful technique in certain situations. Its main purpose is usually to avoid a stalemate and win, or induce a stalemate and draw. I will explain both use cases.
1) White to win:
The white pawn must be promoted to avoid capturing that would result in a draw. However, 1. c8♕ or 1. c8♖ would pin the black bishop and cause a stalemate, while 1. c8♘ doesn’t help either because Black would simply move the bishop to avoid 2. ♘b6#. So, the only way to win is to create a bishop. After 1. c8♗! ♝a7 (or anywhere else) 2. ♘d7 ♝g1 (or elsewhere), White ends the game with 3. ♗b7#. Note that after the second move, both the white knight and the white bishop stand on white squares, so the black bishop cannot threaten them in any way.
2) White to draw:
The pawn must be promoted or White quickly loses. Both 1. b8♕ and 1. b8♖ lose after capturing the knight on c8, and 1. b8♘ is a losing move as well after 1. … ♜cxc8 (Beware, 1. … ♜gxc8 would be a stalemate!). But only 1. b8♗! pins the black rook on c7 and ensures a draw because 1. … ♜xc8 pins the bishop (a queen could still capture the rook), ergo a stalemate.
Promotion to a rook
Promoting to a rook is the least common underpromotion, as it is often less useful than promoting to a knight or bishop. However, in certain situations, promoting to a rook can be a powerful move, such as when the rook can be used to avoid a stalemate. Have a look at one of the best-known chess endgame studies, named after the Spanish priest Fernando Saavedra, who lived in Glasgow during the late 19th century.
In conclusion, underpromotion is an intriguing and strategic aspect of chess that can offer unexpected opportunities and surprise the opponent. While promoting to a queen is typically the most advantageous move, underpromotion to a knight, bishop, or rook can be a valuable option in certain situations. Knowing when to underpromote can be a crucial skill for any chess player, as it can make the difference between winning and losing a game.