Babson task

The Babson task is a chess composition construction built from four alternative branches of the solution. In each variation, Black promotes a pawn to a different piece, and White must respond by promoting a pawn to exactly the same kind of piece in order to achieve the composition's stated goal.

The four correspondences

• Black queen, followed by White queen.
• Black rook, followed by White rook.
• Black bishop, followed by White bishop.
• Black knight, followed by White knight.

Promotion occurs when a pawn reaches the last rank and becomes a queen, rook, bishop, or knight. Choosing a rook, bishop, or knight instead of the usual queen is called underpromotion. In a complete Babson, every matching response must be necessary: after a particular Black promotion, choosing a different White piece fails to achieve the stated goal.

The four promotion pairs do not occur one after another in a single game. They belong to separate branches of the solution created by Black's different defenses. The task is named after American composer Joseph Ney Babson, who proposed it in 1884, and it can appear in different kinds of compositions. Sharing the theme with another work does not by itself create anticipation; that requires an earlier identical composition.