This puzzle comes from IM Andras Toth's book Exploration in Chess Beauty, and is one of my favourites.
|Mate in 11|
G. Murkisch, 1969
The solution can be seen by highlighting the area below.
1.Ke7 Bb4+ 2.Kf6 Bc3+ 3.Kg5 Bd2+ 4.Kh4 Be1+ 5.Qf2!! Bxf2+ 6.Kg5 Be3+ 7.Kf6 Bd4+ 8.Ke7 Bc5+ 9.Kd8 Bb6 10.Kc8 Bxc7 11.Bxc8#
The king makes the seemingly pointless walk from d8 to h4 all so that that the queen can lure the bishop onto a different diagonal, the point of which only becomes relevant when it makes it to b6: it blocks the queen from being able to defend the rook and prevent mate.
A lovely piece of work that demonstrates with real elegance how what seem like the finest, most intricate details of a position can make such an important difference.
Reminiscent of a certain mate in 271 I saw once...
Composed by Nenad Petrovic, 1969.