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Openings › Mate in one › January 2026 › Exercise 4 of 4

Mate in one: Black to move (exercise m1-1919cbd06a)

Black to move and mate in one. In this position Black can give checkmate with one move. The position comes from a rated Lichess game of January 2026.

Last move: 26.Ka3 (White's king from b3 to a3); its two squares are marked on the board.

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Pick a piece, then its square. Keyboard: Tab to the board, arrow keys to move, Enter or Space to pick.

Hint 1: which piece?

Look for a queen move or a bishop move.

Hint 2: which square?

A mating move goes to b4 or b2.

Show the solution

Two moves give checkmate:

  1. Qb4# (b5 to b4). After this move, the black queen on b4 gives check to the white king on a3, and White has no legal move: checkmate. The white king on a3 has no safe square to go to (a2, a4, b2, b3 and b4). Its own pawn on a2 stands in the way. a4 is covered by the black queen on b4. b2 is covered by the black queen on b4 and the black bishop on f6. b3 is covered by the black queen on b4. The black queen on b4 cannot be captured: the king may not take it, as the black pawn on c5 guards b4. The black queen on b4 stands right next to the king, so nothing can be put in between.
  2. Bb2# (f6 to b2). After this move, the black bishop on b2 gives check to the white king on a3, and White has no legal move: checkmate. The white king on a3 has no safe square to go to (a2, a4, b2, b3 and b4). Its own pawn on a2 stands in the way. a4 is covered by the black queen on b5. b3 is covered by the black queen on b5. b4 is covered by the black queen on b5 and the black pawn on c5. The black bishop on b2 cannot be captured: the king may not take it, as the black queen on b5 guards b2. The black bishop on b2 stands right next to the king, so nothing can be put in between.

Our code tried every legal move of Black in this position: these are the only moves that give checkmate.

The position as text

Where this exercise comes from

The position comes from a rated game in our sample of the Lichess open database (CC0 1.0), from the monthly file of January 2026. From a game that began with the Sicilian Defense: Old Sicilian. In that game Black gave checkmate with the next move. We show no player names and no link to the game. Our code tried every legal move of the position and lists every move that gives checkmate; the list, the hints and the explanations are checked again each time the site is built. How the exercises are chosen: Mate in one and How it works.