lachesisq vs Casper

White played 28.axb6, the a‑pawn captured the black rook on b6. The capture removes the only undefended black piece, wins the exchange and creates a passed pawn on b6. After the move the material balance shifts in White’s favour (rook up) and Black’s immediate threat – the knight on c5 eyeing e4 – is still present but no longer compensated by the lost rook. White’s own rook on a3 and pawn on c2 remain undefended, but they are not immediately exploitable.

The engine marks axb6 as the only correct continuation because it converts a tactical opportunity into a concrete material gain. Any alternative (e.g., 28.Bc5 or 28.Rc1) would leave the rook on b6 alive and allow Black to maintain the exchange advantage. After axb6 Black’s best reply is 28…Rb8, trying to activate the remaining rook, but White already emerged a rook up. The move also eliminates the black rook that could later support the knight’s jump to e4, thereby reducing Black’s counterplay.

Take the undefended piece: When an opponent’s piece is hanging, capture it even if it means moving a pawn away from its original file. Material gains outweigh temporary positional concerns.