It’s best to think twice before moving pawns that form the king’s shelter, but often people play f2-f4 (f7-f5) in order to gear up their rooks and f pawns against the opponent’s king. Unfortunately that weakens the a2-g8 (a7-g1) diagonal. So whenever your opponent plays such moves you should think about possibilities of smothered mate, a Greco mate or the mate along the h file, as usually the king hides on h8 (h1) after a check along that diagonal.
Sidney Paine Johnston against Frank James Marshall in 1899
Q: In this position Marshall has weakened the a2-g8 diagonal but on the other hand it is closed by the e6 & d5 pawns. So White played 11.cxd5 and black replied with 11…exd5 as Marshall was relying on the discovered attack after White’s Nxd5.
Was it a good idea?
It turns out to be a bad one because White’s light square bishop can use it with devastating effect. Please try to calculate this position yourself first then check what happened in the game:
Opening up the diagonal.
I think black missed this intermediate move now white is ready to use this diagonal. If 13.Nxd4 then Black gets satisfactory game after 13…Bxd5
Here Black has to surrender the piece in order to prevent himself from immediate loss.
Now what? Can you checkmate Marshall in few moves?
This double check leads to checkmate
16. Ng6+ hxf6
Opening up h file leads to mate on next move
Here White has sacrificed the knight in order to open up h file which is very common with this theme.