Selfmate

A selfmate is a chess problem in which White, moving first, must force Black to deliver checkmate within a specified number of moves. Selfmates were once known as sui-mates.

The problem shown is a relatively simple example. It is a selfmate in two by Wolfgang Pauly from The Theory of Pawn Promotion, 1912: White moves first and compels Black to deliver checkmate on or before Black's second move.

If White can leave Black with no option but to play Bxg2#, the problem is solved.

The only move by which White can force Black to deliver checkmate on or before move two is:

From the ensuing position, Black only has two legal responses, from which White can subsequently force the selfmate:

Note that only a promotion to a knight works on move one: any other piece would be able to interpose after 1...Bxg2+.

The current record for the longest selfmate problem is a selfmate in 203, composed by Karlheinz Bachmann and Christopher Jeremy Morse in 2006. The puzzle is based on a 1922 342-move composition by Ottó Titusz Bláthy, which was later found to be cooked.^{[citation needed]}

Prior to December 2021, the record for the longest selfmate problem was a 359-move problem, created by Andriy Stetsenko in 2016. Unfortunately, this problem was later found to be cooked, as a shorter solution exists.