Openings › Mate in one › June 2026 › Exercise 3 of 4
Mate in one: Black to move (exercise m1-2ecb4da20a)
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 June 2026.
Last move: 27.Kb4 (White's king from c4 to b4); its two squares are marked on the board.
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 pawn move.
Hint 2: which square?
The mating move goes to a5.
Show the solution
One move gives checkmate:
- a5# (a7 to a5). After this move, the black pawn on a5 gives check to the white king on b4, and White has no legal move: checkmate. The white king on b4 has no safe square to go to (a3, a4, a5, b3, b5, c3, c4 and c5). Its own knight on a3, pawn on b3 and pawn on c3 stand in the way. a4 is covered by the black pawn on b5. c4 is covered by the black pawn on b5. c5 is covered by the black king on d6. The king may not take the black pawn on b5: the black pawn on c6 guards b5. The black pawn on a5 cannot be captured: the king may not take it, as the black rook on a8 guards a5. The black pawn on a5 stands right next to the king, so nothing can be put in between.
Our code tried every legal move of Black in this position: this is the only move that gives checkmate.
The position as text
- Black to move.
- Last move: 27.Kb4.
- White: king b4; rook a1; bishop c1; knight a3; pawns a2, b3, c3, d4, g2.
- Black: king d6; rook a8; bishop f5; knight g4; pawns a7, b5, c6, e5, g7.
- Castling: no longer allowed for either side.
- FEN:
r7/p5p1/2pk4/1p2pb2/1K1P2n1/NPP5/P5P1/R1B5 b - - 1 27
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 June 2026. From a game that began with the Italian Game: Two Knights Defense, Traxler Counterattack. 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.