A seriesmover refers to a chess problem where one side executes a consecutive sequence of valid moves without any response from the opposing side. The sequence culminates with the other side performing a single move that results in either a checkmate or a stalemate, depending on the specific conditions given in the problem.
The objective of the move sequence can vary, leading to three distinct types of chess problem stipulations: series-mate, series-helpmate, and series-selfmate. In each case, the player conducting the sequence must avoid moving into a position of check at all times. Additionally, issuing a check during the sequence is not allowed, except on the final move.
Allow me to introduce a fascinating chess study created by Theodor Steudel in 1997. This particular study serves as an excellent illustration of a series-mate puzzle, where chess pieces must work in harmony to protect their king from being checked during the sequence.
White to move and deliver a series-mate in 13.
It’s obvious that the b2-pawn is pinned, so White must either start the sequence with a king move, or coordinate the pawn moves to keep the main diagonal always blocked by at least one piece. The first solution isn’t possible because of the move count limit (cannot exceed thirteen), so let’s proceed with the latter:
1. d4 2. b4 3. b5 4. b6 5. b7
Considering the restrictions in the problem (prohibiting issuing a check during the sequence), the pawn is unable to promote to a queen or a rook. Moreover, promoting to a bishop would not be advantageous, as even two bishops together would be insufficient to achieve checkmate without their king’s assistance. Consequently, the only viable choice is to promote the pawn to a knight.
6. b8=♘ 7. ♘d7 8. ♘f6 9. d5 10. d6 11. d7 12. d8=♘
We made it. The final move will checkmate the black king: 13. ♘f7#