2024/09/22 DPA: "g8 To h8 In A Roundabout Way"

White to move:

White obviously is in trouble due to the Black pawns.

White has the potential for a simple Rook mate but the King would have to be on f7 and the Rook would have to be able to get to the h file away from the Black King.

White's King must stay off the a1-h8 diagonal because of ... a1(=Q)+.

1. Ra8 b2  2. Rxa2 b1(=Q)  3. Rh2 Kg6 and the King escapes.

1. Rg7+ Kh8  2. Ra7 b2  3. Rxa2 b1(=Q)  4. Rh2+.

The difference is that Black cannot escape to g6 since he was forced back to h8.  4. ... Kg8 is his only move.  But what's the follow-up?

1. Rg1 b2  2. Kf7 b1(=Q) and 3. Rh1# fails due to ... Qxh1.

But White can't lead with 1. Rg2 due to 1. ... a1(=Q)

Is there any reasonable first move other than 1. Rg7+ that doesn't lose tempo?

1. Nf7 protects the Rook but 1. ... a1(=Q) now guards g7.

1. Nh6 loses the Knight.

1. Nd4 attacks the b pawn but allows the a pawn to promote.  It also leaves the Rook undefended.

So Knight moves are out.

King moves don't seem to help after 1. ... a1(=Q).

So I think it's a Rook move and the only one that holds any promise is 1. Rg7+ but I'm far from confident I'm correct.

OK, I played 1. Rg7+ and it was correct; 1. ... Kh8 is forced.

Now what?

Still no good King or Knight moves.

The Rook move should prevent the a pawn from promoting.  Rg1 and Ra7 are the only ways.

The drawback of 2. Rg1 is that it doesn't attack either pawn and allows 2. ... b2, threatening to promote with support.  Whereas 2. Ra7 b2  3. Rxa2 at least wins a pawn.

But the other pawn will promote so maybe the purpose of 2. Ra7 is not to capture a pawn but to allow for the Rook to reposition itself.

Where?  Not on the 7th rank because it could have moved anywhere on the 7th rank the previous move.  So it must be along the a file.

3. Ra4, Ra3, and Rxa2 all give the chance to slide over to the h file.  But how are any of them different from each other?  If this is the right idea, why does one work and the other 2 fail?

I couldn't see it.

..

The key was recognizing the need to drive the King back with 1. Rg7 and then prevent the a pawn from promoting and set up an eventual h file check with 2. Rg1. 

Kf6 prevents ... Kg7 and forces Kf8 which leads to the Knight check and Rook mate.

Also, White had to check with Rh1+ before Black promoted because otherwise, Black can capture the Rook.

Note that Black can never promote with check since the b2 pawn blocks check from a Queen on a1.