When to not promote to a Queen?

The Promotion Conundrum

Anyone who has been playing chess for even a little while understands that it is usually better to promote to a queen. The queen is the most powerful piece on the board, so why settle for less upon promotion? The reality is that sometimes, as we will see in this article, we have to promote to a piece other than a queen.

First off, however, lets review exactly what promotion is. If your pawn reaches the eighth rank (or, if black, the first rank), you are required to immediately remove that pawn from the board and replace it with one of the following pieces: Queen, rook, bishop or knight. Commonly, promoting to a queen is known as “queening” and promoting to any other piece is called “underpromotion.” If the piece you want to promote to is still on the board (i.e., your opponent did not capture it earlier in the game), you should stop the clock and summon a tournament director to find an extra piece for promotion.

For the purposes of the touch-move rule, your choice of promoting piece is fixed when the piece touches the promotion square, rather than when you touch the piece. Also, a promotion can give check and block check. Finally, there is no connection between what pieces are on the board and the promotion, so it is allowed to have two or more queens, three or more knights, etc.

Knight Promotion

The most common piece you may need to underpromote to would likely be the knight. Why? The main reason is that the queen can use both the moves of a rook and a bishop. By contrast, a knight can do what the queen cannot. It moves in an L-shape (e.g., two squares up/down and one square sideways, or, one square up/down and two squares sideways) and is the only piece on the board that can hop over other pieces.

Accordingly, most knight promotions revolve around using the knight’s ability to move in ways the queen cannot. Here is an example that shows how important the difference between a queen promotion and a knight promotion can be:

The difference between these two options is astronomical. In the first option, after you promote to a queen, black’s queen instantly checkmates white’s king. In the second option, white’s promotion to a knight puts black in check (forting the queen in the process), which requires black to move his king and empowers white to capture black’s queen. As long as white does not blunder in the following moves, he will win in the second option. Thus, we see that one way in which a knight promotion could be preferred is if it checks the opponent’s king and such check is essential to the position, as it was here.

Another case in which a knight promotion might reasonably be invoked would be to avoid stalemate (i.e., where either player has no move but is not in check). An example of this possibility is as follows:-

Neither of these options suffers white defeat. Promoting to a queen, however, results in immediate stalemate. A rook promotion has the same effect. By contrast, promoting to a knight enables white to secure a win if he plays perfectly. Stockfish indicates that, with perfect play by both sides, the soonest checkmate could occur would be is within fifteen moves. Again, we see that the difference over choosing a queen or a knight decides what the result of the game will be.

Rook Promotion

The instances in which someone who promotes to a rook are significantly less than for a knight. In the case of a rook, the only reason that such a promotion would occur is if you needed to avoid stalemate. What would rook promotion look like? The following example demonstrates how rook promotion might debar stalemate:

We again see the question of whether to promote to a queen or a lessor piece altering the result. The first option immediately incurs stalemate. In the second, white obtains a substantial material advantage while not drawing the game in the process, which empowers white to easily secure checkmate eventually.

Bishop Promotion

The rarest form of underpromotion is promoting to a bishop and is only necessary to protect against stalemate. One reason why bishop promotion is so rare is simply that the sort of positions where promoting to a queen, rook or knight all result in stalemate are very rare. While these positions are extremely rare, they do exist, as the following position demonstrates:-

When you promote to either a queen or rook in this position, black’s king cannot move because he is landlocked by his pawns and the dominating rook. To succeed in this position, white must promote without barring black’s king from entering the G file, which can only be achieved by a knight or bishop promotion. In this case, knight promotion fails because the knight cannot passively protect the a2 pawn (when black’s king arrives to that area of the board, he can require the knight to constantly move around, leading to a draw by the 50-move rule).

Therefore, white must promote to a bishop to secure victory. After g8=B, g3 and Be6, black is forced out of the corner and white can capture black’s pawns. Following the capture of those pawns, white can take his time making his way to black’s a3 pawn. Eventually, the game transposes into a position (as shown above) where white captures the a3 pawn and advances his pawn to the promotion square. Considering that white can control the promotion square with his light-colored bishop (i.e., a dark-colored bishop would be a draw), the pawn will promote to a queen and black will soon thereafter suffer checkmate at last.

Conclusion

What is the point of all these positions? Nothing in this article was intended to demonstrate how to deal with underpromotion if you ever need it. It was too short for that. Rather, my intention is to convey a simple and unforgettable point: Always check if an underpromotion is necessary, or at least more ideal, than promoting to a queen before you ever determine what piece you will promote with. Look at all of your promotable pieces (knight, rook and bishop), not just your queen. While promoting to a queen is often a clear sign of victory, it is sometimes the case that you need to promote to something other than a queen to truly clinch victory.

Bibliography: USCF Official Rules of Chess (7th Edition), 2019, Chapter 1.

Photo Credit: https://en.wikipedia.org/wiki/Ad%C3%A9lie_penguin#/media/File:Adelie_Penguins_on_iceberg.jpg