# A chess problem question: Why is this the solution?

``````[FEN "5B2/3p1n2/R2p4/1P1NRBQ1/1KPkrb2/1p6/2Pp1Pn1/4r3 w - - 0 1"]

1. Nc7! Rxe5 (1... Nxg5) (1... d1=Q) 2.c3#
``````

What would make you play Nc7? This results in checkmate in 2 if, as the computer does, Rxe5 is played. But why wouldn't the computer just play Nxg5, winning the queen and preventing checkmate? Or why not play to d1 and promote to a queen?

What would make you play Nc7?

It is the only move with which White can give check mate in two moves.

This results in checkmate in 2 if, as the computer does, Rxe5 is played, but why wouldn't the computer just play Nxg5, winning the queen and preventing checkmate?

On `1. ...Nxg5` White plays `2.Rd5` which check mates.

Or d1 and promote to a queen?

On `1. ...d1Q` White plays `2.Rd5` which check mates.

## SUMMARY:

1.`Nc7` has been played to free the rook on `e5` to give check mate, by coming to `d5`.

This is why computer played `1. ...Rxe5`, since on every Black's move `2.Rd5` check mates, except for these:

`1. ...Ne3` but then White mates with `2.Rxe4`.

`1. ...Nxe5` where White mates with `2.Rxd6`.

`1. ...Bxe5` where White mates with `2.Qxd2`.

`1. ...dxe5` where White mates with `2.Bc5`.

`1. ...Kxe5` where White mates with `2.Bg7`.

Best regards.

• You forgot the most important thing ;-), i.e. that this is a chess problem, which simply has different rules than an OTB game (for this example, the problem asks not for any win, but for the unique 2#). This usually confuses the novice. Mar 4, 2021 at 10:33