2025/11/16 DPA: "Tight Quarters And Only One Way Out"

White to move:

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This was one of my submissions so this blog will not be real-time [although it took me a while to remember the solution and why no defence works].

Black's King only has h5.

If White could force Black to play ... Rxh8, then Qxh8 would be checkmate.

But White can't force this.  If 1. Rxh7 Kxh7, White can't get to h8.

And the Black Queen threatens to come to the rescue with ... Qe7.

White's also down a piece and he doesn't control the dark squares.  Fortunately, Black does not have a DSB for defence.

If White could play 1. g4 then 2. g5+ Kh5. 3. Bf3+ Bg4/Kxh4. 4. Rxh7#.  But 1. g4 is met with 1. ... Bxg4.  And there's no way to guard g4 by first playing 1. Kh3 due to Black's Bishop guarding that square.

White does have time for a setup move, though, as Black has no checks.

But if 1. Bh3, to try and remove Black's Bishop in order to play g4 then g5 [and also, note that if Bxf5, Black cannot recapture due to the pinned pawn], then Black can counter with 1. ... Qxa2+.  White can retreat his Bishop but if so, why bother moving it in the first place?

White can also retreat the King but now the Black Queen can go check-happy.

Or Black could simply defend with 1. ... Qe7, which looks even better.

If White can attack the Rook a 2nd time, then Qxh7#, as g5 is covered by the h pawn.

But how does White make that happen?

1. Qf7 [Black's Rook is pinned and so cannot capture the Queen] allows 1. ... Rxh8.

Note that 1. ... Qe7??  2. Rxh7#, relying on the Lead Shield concept of the White Queen blocking the Black Queen's X-Ray defence of the Rook so that 2. Qxh7+ Qxh7 saves the day.

White doesn't want to play 1. h5, again, due to 1. ... Qe7.

1. Qg5+ allows 1. ... Kg7.

1. Rg8, to prevent 1. ... Kg7, still allows 1. ... Qe7, which X-Ray defends g5, making 2. Qg5+ unwise.

White has to find a move that negates the effect of 1. ... Qe7.

There's no check that works.

What White has to see is the one-two combination of 1. g4, threatening 2. g5 and checkmate to follow, encourages 1. ... Bxg4 [if 1. ... Qe7. 2. Qxe7 Rxh8  3. g5 Kh5. 4. Kg3 leads to mate but 1. ... Qe7 leads to multiple winning solutions and so won't be chosen for a puzzle] but then makes 2. Rg8 the killer follow-up:  not only does it remove g7 as an escape, it also simultaneously threatens 3. Qxg6#, because Black's Bishop is no longer guarding g6.

The only way to guard against this is 2. ... Bf5, which allows 3. Qg5#.

This also makes 2. ... Rg7 ineffective:  3. Qxg7+ Kh5. 4. Qh7/Rh8#.  Why does this work now but not if the immediate 1. Rg8?  Because Black's Bishop on g4 blocks the King from escaping the h file check [and it can't capture the h pawn because it's X-Ray defended by the Queen or Rook [whichever piece delivered check].

This is a ZAS [Zombie Attack Scenario]:  White threatens two checkmates and Black can only defend against one, which allows the other.  

In the same way, the enemy is trapped in a room with doors at both ends with no locks and Zombies closing in:  he can bar one door or the other but not both.

This puzzle came from Carlsen v Additya, Titled Tuesday Grand Prix 2025, hypothetical.

Black could instead play various Queen moves instead of 1. ... Bxg4 that all lead to checkmate as well.  The puzzle solution was the one highlighted in the commentary so that's the one I chose.

A deceptively complicated puzzle, with many variations to consider.

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1. g4 threatens 2. g5+ and checkmate to come.

2. Rg8 threatens 3. Qxg6#.

3. Qg5#.