Now let’s have a look at some famous positions where spectacular moves were made to reach the general pattern we are examining here. We begin with consecutive positions from the game Blackburne-Schwartz (1881). Here White plays 1. Bf6, preparing the possibility of mate in two different ways. With his bishop now on the long diagonal he threatens to play Qh6 and then mate with the queen a move later on g7 or h8. He also has the more remote threat of pushing his rooks down the h-file in the manner described a little earlier: 2. Rxh5, g6xR; then 3. Rxh5 again with 4. Rh8# coming next. The rooks can’t quite carry this off by themselves, because after White’s second rook captures on h5 Black can interpose his knight on g7 and so block the White bishop’s path to h8. But then White has another resource: again he can bring in his queen at h6 and mate a move later.

All these are just ideas. The point is that with Bf6 White gives himself a powerful bishop on the long diagonal with three pieces that might be able to pitch in on the h-file if Black doesn't respond adequately. You should not assume that even so strong a player as Blackburne, one of the greats of the 19th century, thought he knew for sure how his opponent would reply. More likely he saw that he had a threat that improved his position without creating any problems, so he played it.

Black’s best reply to 1. Bf6 probably is to retreat his own dark-squared bishop to f8. This way it attacks h6 and so prevents White’s queen from landing there; and if White tries to blast his way to h8 by repeatedly capturing on h5 with his rooks, Black has the simple Bg7, blocking the path of White's bishop to h8 and thus stopping the mate. Be7 is another plausible move for Black here, directly attacking White’s troublesome bishop on f6.

Black replied to Bf6 with a different move that also seems strong: Nf4+. This forks White's king and the loose bishop on d3, and with plenty of protection from the bishop on d6 and the queen behind it. The move also adds a reinforcement to the h5 pawn, giving Black another way to capture on that square if White tries to force his way down the file with his two rooks. Finally the knight also blocks the White queen’s path to h6 (and with protection from the bishop on d6). So what would you play next as White? Read on.