Underpromotion
The theme of underpromotion in chess has very distant roots. It is extremely spectacular and so study composers make great use of it. Generally, these are positions in which the canonical promotion to a Queen produces a stalemate. Being rather rooted in the concept that once you reach the eighth rank with a Pawn, you turn it into a Queen, that is, in the strongest possible piece, often the opportunity of promoting to a different piece is being missed. In practice, it is not an instinctive move.
Initially, however, the promotion rules were different from the current ones.
The basic idea was that a modest soldier, if he was able to penetrate the enemy lines all the way through, had to have a military promotion as a prize. Initially the Pawn had to become a Ferz, a piece no longer existing, that moved diagonally by only one square, but then it was realized that it wasn't much of a promotion. So something of more substance had to be devised.
Consequently, for a certain period, the rule said that the piece could not be chosen by the player, but had to be that of the Pawn column (for example, the promotion of the a-Pawn had to be a Rook). In the case of e-Pawn (the King's column), the promotion was to a Queen.
Later, another change occurred, consisting in the promotion to a piece previously captured by the opponent, thus making it impossible for two Queens of the same color to appear on the board. If the opponent had not yet captured a piece, the promotion was to be deferred.
A statistical study performed in 2006, revealed that in real games about 97% of promotions was to a Queen, and therefore only 3% was an underpromotion. In addition, many of these were not strictly necessary but only "for the show". Among them, the least used was that to a Bishop.
The most famous underpromotion in history is perhaps that of Saavedra, a Spanish father of the Catholic religious order of the Passionists (1847-1922) who discovered a winning sequence, in a position considered a draw, thanks to underpromotion.
Those who do not know it can give it a try at the position of the diagram:
Precisely because of the continuous modification of the rule, creative minds have produced unimaginable things. For example, in 1862 Johann Löwenthal created a study in which the only salvation is the promotion to ... a Pawn!
In fact, White is forced to capture the Black Rook, but any promotion loses due to 1 ... gxh3 and mate to the next move. On the other hand, after the promotion to a Pawn, Black cannot prevent the stalemate or, by moving the Bishop, allow White to capture the Pg2 with consequent draw.
Or the following one that takes advantage of a trivial flaw in the regulation. White moves and mates in one move:
Due to the ancient rules of chess, promotion was exclusively referred to a piece of one’s own choice, but only implying the color equal to that of the Pawn; that is, it was not explicitly established that it should be a piece of the same color as the Pawn. It was therefore possible to promote to a piece of a color other than one's own Pawn. So, White mates in one move promoting to a Black Knight!
Finally, let's go back to a standard problem. This is the famous problem of James Plaskett, an English GM who proposed it at the 1987 Brussels tournament.
Both colors can promote - which will be the right promotions? It is said that of all the GMs present at the tournament to which it was submitted, only Tal managed to solve it.
Knowing what the Wizard of Riga was capable of, it is possible that it is not just a legend!
