The sacrifice on f7

The key idea

Bxf7+ isn't the strike: it's the strike's first move. Before touching f7, have the follow-up check identified, and what you get from it. If after the king recaptures you don't have a check that wins material or nets something, you're giving away a bishop for a pawn.

Example 1 · The strike with a payoff behind it

Pirc Defense: Black has just played the knight to d7 without looking at f7. That knight blocks the queen's only escape square — and that turns the strike into a collection operation. White to move.

1. Bxf7+ The strike. And before delivering it, the count has been made: after the king recapture comes Ng5+, and then the knight lands on e6 attacking the queen. That's the payoff. Without that script, this move doesn't get played.
2. Kxf7 Accepting is the natural choice — declining leaves White with a clean extra pawn and the black king out for a stroll. The king is already out of the house, which is exactly what was wanted.
3. Ng5+ The check that was in the script. Without this check, the sacrifice doesn't exist: it's what wins the tempo to get the knight to e6.
4. Kg8 The king goes back home, which is the best it has. Staying in the center with Ke8 is even worse: the knight goes to e6 all the same and the engine's advantage for White doubles.
5. Ne6 Here's the payoff. The knight attacks the queen on d8, and look at the escape squares: c7 is covered by the knight itself, d7 is occupied by the knight Black just moved, e7 is covered by its own pawn. Only one is left.
6. Qe8 The only free square. The queen saves itself… and lands on the very same diagonal as the rook on a8.
7. Nxc7 Double attack: the knight attacks the queen again and the rook on a8. The queen has to move and the rook is left alone.
8. Qd8 Forced.
9. Nxa8 And the rook is won. Tally: White gave up a bishop (three points) and collected a pawn and a rook (six), with the black king never able to castle. The engine rates the position at more than two points. That's a strike on f7 with a script: the gain was calculated before touching the bishop.

Example 2 · Same diagonal, no script behind it

Textbook Italian. The bishop eyes f7 exactly as in Example 1, the king defends f7 exactly as in Example 1… and here Bxf7+ loses the game. Compare the two boards before touching anything. White to move.

1. O-O White does NOT strike, and rightly so. Run the count from Example 1 on this board: after Bxf7+ Kxf7 there's no Ng5+ that wins anything (the knight on f6 covers that entry square), there's no black queen to trap, and there's no invasion square at all. The bishop would have gone for a single pawn: the engine rates it at three and a half points for Black. So, normal chess — king goes home.
2. O-O Black does the same. A healthy game for both sides.
3. h3 A useful move, the kind that actually wins games: it takes the g4 square away from the black bishop before it can use it.
4. a6 Black does the same on their own flank.
5. a4 Space and prevention on the other side of the board.
6. h6 And the position stays balanced, both structures healthy. The moral of this pair of examples: the diagonal toward f7 is the same on both boards; what changes is what's BEHIND it. With a script, the strike pays for itself. Without one, the game is over before move ten — and on the wrong side.

Practice

You have White. The black knight has just landed on d7 and taken away its own queen's escape square. Carry out the full strike on f7, all the way to winning the rook.

1. The strike, with the script already learned: bishop for pawn, and the knight check already waiting in the chamber. The point only the king defends. But before touching it, look at the next move: what check do you have ready?
2. There's the check that wins the tempo. Without it, the sacrifice would be worth nothing. Give the knight check that pushes the king and clears the way to e6.
3. The payoff: the black queen is attacked and you've blocked off almost every one of its exits with its own pieces. Put the knight on the square from which it attacks the black queen. Count its escapes first: there are barely any.
4. Double attack: queen and rook at once. The queen saves itself, the rook doesn't. Not with check, but with a double attack: there's a square from which you attack both the queen and the rook on a8.
5. Rook won. Bishop given up, pawn and rook collected, and a black king that won't castle for the rest of the game. The strike on f7, carried out with its full script. Take the rook in the corner.

The strike on f7 seen from both sides: the collection operation when there's a script behind it, and the giveaway when there's only a pretty diagonal. Take the question with you and always ask it before touching the bishop: after the king recaptures, what check do I give, and what do I get from it? If you don't have an answer with a name and a face, keep the bishop.