Openings › Mate in one › December 2025 › Exercise 4 of 4
Mate in one: Black to move (exercise m1-ee01c41e01)
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 December 2025.
Last move: 37.Kg3 (White's king from h3 to g3); 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 rook move.
Hint 2: which square?
The mating move goes to g2.
Show the solution
One move gives checkmate:
- Rbg2# (b2 to g2). After this move, the black rook on g2 gives check to the white king on g3, and White has no legal move: checkmate. The white king on g3 has no safe square to go to (f2, f3, f4, g2, g4, h2, h3 and h4). Its own rook on f4, pawn on g4 and bishop on h4 stand in the way. f2 is covered by the black rook on g2. f3 is covered by the black knight on d4. h3 is covered by the black rook on h2. The king may not take the black rook on h2: the black rook on g2 guards h2. The black rook on g2 cannot be captured: the king may not take it, as the black rook on h2 guards g2. The black rook on g2 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: 37.Kg3.
- White: king g3; rooks f4, f8; bishop h4; pawns a2, g4.
- Black: king g6; rooks b2, h2; knight d4; pawns a7, b7, c4, h7.
- Castling: no longer allowed for either side.
- FEN:
5R2/pp5p/6k1/8/2pn1RPB/6K1/Pr5r/8 b - - 12 37
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 December 2025. From a game that began with the Pirc Defense. 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.