subqueens

A subqueen is a term used in certain chess problems and compositions to refer to a queen that has been created through pawn promotion, specifically when a pawn reaches the eighth rank and can be promoted to a queen. This is in contrast to a queen that starts the game on the board. The concept of subqueens is important in the analysis of chess problems where the creation of a new queen through promotion is a key element of the solution.

In chess, a pawn that advances to the opponent's back rank has the option to be promoted to any other piece except a king. While it can be promoted to a knight, bishop, or rook, promotion to a queen is usually the most advantageous due to its powerful movement. Therefore, when a pawn reaches the eighth rank, it is often promoted to a queen, and this newly created queen is sometimes referred to as a "subqueen."

The presence of subqueens can significantly alter the strategic and tactical landscape of a chess game or problem. Their introduction can lead to new mating threats, defensive resources, or material advantages. In chess composition, the clever use of subqueens is a common theme, and problems are often designed to showcase surprising or elegant ways in which subqueens can be used to achieve a specific outcome, such as a checkmate in a certain number of moves. The term emphasizes the "secondary" nature of this queen, as it was not part of the initial setup.