levonaronian vs iwanyu

White played 39.Bg6, moving the bishop from f5 to g6. The move eliminates the completely undefended bishop on f5, attacks the black knight on h7, and keeps the pressure on the black pawn on f6 (still threatened by the bishop on e5). After Bg6 the board features a double threat: Bxh7 (winning the knight) and Bxf6 (winning the pawn). Black still threatens ...fxe5, which would capture the bishop on e5, but White now has the initiative and the opponent's key pieces on b7 and d1 are also undefended.

Bg6 is superior because it simultaneously solves a tactical liability (the undefended bishop) and creates concrete threats. Any alternative such as retreating the bishop or defending the pawn on f6 would leave the bishop on f5 hanging and give Black time to play ...fxe5, winning a piece. By placing the bishop on g6 White forces Black to respond to the immediate danger to the knight on h7; the engine’s best reply, 39...Rd7, merely defends the rook and prepares to meet the threats, but White retains the advantage of the two‑piece attack and the removal of the opponent’s undefended rook on d1. In short, Bg6 maximizes piece activity while preserving material, whereas other moves would either lose material or miss the tactical opportunity.

Eliminate undefended pieces and generate multiple threats: When a piece is hanging, relocate it to a square that both saves it and creates new threats. This forces the opponent to react defensively and often yields a lasting advantage.