Position from the game Zhongyi Tan vs Aleksandra Goryachkina, Semifinals of the World Cup 2023 Women’s Section
Solution
Bb4!
If white responds with Rxb4, black can simply promote with a discovered check b1=Q+, and captures the rook on the next move.
If white doesn’t take the bishop, black can safely promote the pawn because it is covered by the bishop.
I was thinking along the lines of Bxf4. Would that have the same result?
I think if you do that white has a path to victory. You lose the bishop, still can’t queen your pawn, and white can now pressure your king position.
The move here is genius because it literally locks up the game.
Not arguing - I truly want to understand. Black risks the bishop either way, and white can also check the black king either way, n’est-ce pas?
Right now black can’t promote their pawn without losing it, as soon as he tries, white takes it. Blocking it with the bishop sets up the only situation where the new queen is a factor in the game… Which happens to be a checkmate in 2 moves.
Any other move and I’d bet white wins
Right, so moving the bishop allows black to discover check with the rook by promoting the pawn. It’s not quite mate in two because white can delay the inevitable by covering its king with the knight.
My question is, why is it better to move the bishop to b4 than to take the pawn at f4?
Couple reasons I think of.
1 is you lose your bishop to the white pawn next. Then the King has more mobility to get away from your queen/rook
And, you still haven’t broken the stalemate of the white rook keeping your pawn from promotion. White just never moves the rook and black can’t move his rook and that leaves a knight and two pawns against a king and two pawns… With a white rook covering 7, while the black rook just stares on. The bishop sacrifice at that moment gives black a checkmate in 3 (you’re right not 2).
How do you see it playing out if black takes the pawn?
Here’s a more detailed explanation:
… Bxf4
(There are a couple things white could do here, including taking the pawn at g6+, but nothing that really puts white ahead, because black is eventually looking to promote the pawn for discovered check. White can’t take the pawn with his rook before it’s promoted because he loses the rook. He can’t take the promoted pawn either because he needs to get out of check from the black rook. Uncovering the king by taking the bishop with his pawn would work to white’s disadvantage against a rook-queen attack.)
Then white’s only move would be:
Nf2
Then black could either take the white rook with the new queen or try to maneuver into mate with the rook and queen.
My idea was:
… Bxf4
g3xf4 b1Q+
Ng2
The other way would be:
… Bb4
Rxb4 b1Q+
Ng2
I don’t see a huge difference - black loses - or at least risks losing - the bishop either way, and also is able to promote the pawn either way. The white rook can’t take the new queen because he is in check from the black rook.
My solution opens up the king’s defenses a little and gains black a pawn
