2024/02/09 DPA: "Remove The Guard, Double The Checks"

White to move.

Black has dark square weaknesses.

White controls the d file and f8.

White is down a piece.

1. Ng7+ Kf8  2. Qd8+ Nxd8  3. Rxd8+ Re8  4. Ne6^++# [discovered check, double check, checkmate].

Oops, that's not true:  Black has 4. ... Ke7.  Also, 1. Ng7+ is not forcing enough, as Black can play 1. ... Qxg7.

So change the move order:  1. Qd8+ Nxd8  2. Ng7+ Kf8  3. Ne6^++ [discovered check, double check] Ke8  4. Rxd8#.

The key is the move order:  if White recaptures with the Rook prematurely, it allows Black the saving move ... Re8, which blocks check but also frees up e7.

Double checks are so powerful because they cannot be blocked or captured; the King must move.  The Knight move was great because, not only did it lead to a double check, it also added an attacker to d8.

No, I was wrong:  2. Ng7+ still has the problem of 2. ... Qxg7.

How about 1. Qxc6+ Qxc6  2. Ng7+ Kf8  3. Ne6^++ Ke8  4. Rd8#

Yeah, that was it.

I recognized the problem with Ng7+ for the first move but somehow didn't apply that to the second move, leading to my error.  When I recalculated, I realized I had to get the Black Queen away from guarding g7.  Then the double check works.

The Queen sac [solid blue] deflected the Black Queen from guarding g7 [dashed blue] and also removed the Knight defender of d8, allowing the Knight to check on g7 [green] and then to e6 [green] with the Bishop check [red] and also controlling d8 for the Rook checkmate [yellow].