queen lost in 10 moves. the bishop-knight threat to the white king is nullified by white pawn to a3. any move that doesn't take the bishop at d8 (10. ... O-O or 10. ... Kf8) would be highly disadvantageous to black as 11. Bf6 pins the black king to whatever square it ends up on. capturing the bishop sets up a smother, which could happen multiple ways. white pawn to a3 would have been my next move, and following the the forward bishop's retreat the remaining white bishop would move to b5 and force the threatened knight to either b8 or e7, Ne7 being the weaker move out of the two. assuming Nb8, my rear knight moves to h3. black has no offensive moves, and will probably advance his pawns or retreat his forward knight. i kingside castle and can capture black's f pawn unless it's at f5, which would be the best use of turns for black. assuming black bishop retreated to a5 or c5, white b pawn moves to b4, forcing the bishop to retreat again, with f8 being his best choice. queen captures knight at d4. black's rear knight would threaten my queen if there was any minor piece movement at all, but this would be a mistake as black would be forced to move his rook to safety. black pawn movement would not change anything. queen moves to g7 and threatens kingside rook, to which black must respond by moving it to e8. knight moves to g5, rook pawn threatens, queen captures rook pawn. black cannot move a non-pawn without losing one. knight moves to g7 and can deliver check in one turn. if black moves his bishop at c8 to avoid checkmate, queen captures g file pawn, king to c8, pawn or bishop threatens black bishop and it is trapped at b7 or the bishop which will capture it delivers check; king can only move to b8. white rook captures the pawn on its file. any move black makes will result in white rook to f8, threatening the black rook. black rook captures, white queen captures black rook and checkmates. if the black rook does not capture, the white rook captures the black rook and checkmates.