Lesson
White to move. Main line: 1. Bxh7+ Kxh7 2. Ng5+ Kg8 3. Qh5 Qxg5 4. Bxg5
After 3.Qh5 the threat is 4.Qh7#, and the king has no flight square: g8 is covered by the queen, f8 is occupied by the rook, and nothing defends h7. Black’s least-bad answer is 3...Qxg5, handing back the queen for the knight to stop the mate — which is why the sacrifice is sound rather than speculative.
The checklist is what makes this work, and every item is load-bearing. The e5 pawn denies f6 to any defending knight. The b1–h7 diagonal is clear for the bishop. The knight on f3 reaches g5 in one hop, and vacating f3 opens the d1–h5 route for the queen. Nothing covers g5 — this is the item most often missed. With a black bishop on e7 instead of d7, 2...Bxg5! simply takes the knight and Black stands better.
That is the discipline the position teaches: run the checklist before you play the sacrifice, not after. The recorded defenses cover every practical try — accepting and stepping to g8, stepping back to h8 into mate, running to g6 into a pawn storm, or declining and staying a pawn down with the attack still to come.
If 2...Kh8 (walking into mate): 2... Kh8 3. Qh5+ Kg8 4. Qh7# — the king steps back onto the mating square.
If 2...Kg6 (running forward): 2... Kg6 3. h4 — the pawn joins in and the king has no shelter left.
If 1...Kh8 (declining): 1... Kh8 2. Ng5 — White keeps the extra pawn and the attack arrives anyway.
The classical bishop sacrifice
Bxh7+ is the oldest attacking pattern in the book: the bishop gives itself to pull the castled king onto h7, where a knight check from g5 and the queen arriving on h5 create an immediate mating threat.
It is a pattern with preconditions, and the preconditions are the actual content. Played on intuition it is a piece thrown away; played when the checklist is complete it is close to winning by force.
The checklist, item by item
The bishop needs the b1–h7 diagonal clear. A knight must reach g5 in one move — and vacating f3 opens the queen’s route to h5, so the same move does both jobs. There must be no black knight on f6, which here is handled by the pawn on e5 taking the square away.
The item most often forgotten is the last one: nothing may cover g5. In this position Black’s bishop sits on d7 and the sacrifice is the engine’s top move at around +8. With that same bishop on e7 instead, 2...Bxg5 simply takes the knight and Black is better by two pawns — the identical sacrifice, refuted by one piece placement.
What happens after the king moves
Every king move is covered, and each one fails differently. Stepping back to h8 walks into 3.Qh5+ Kg8 4.Qh7#. Running to g6 meets 3.h4, when the pawn joins the attack and the king has nowhere safe. Accepting and returning to g8 runs into 3.Qh5, and the only defence to mate on h7 is handing back the queen with 3...Qxg5.
Declining the bishop with 1...Kh8 does not solve anything either — White plays 2.Ng5 anyway, a clean pawn ahead with the attack still coming.
1.Bxh7+: The engine’s first choice at roughly +8. The sacrifice is sound here.
2...Kh8: Loses to forced mate: 3.Qh5+ Kg8 4.Qh7#.
2...Kg6: Met by 3.h4, the engine’s top move — the king is hunted in the open.
With a bishop on e7 instead of d7: 2...Bxg5 refutes the whole idea and leaves Black about two pawns better. The checklist is not optional.
Run the four checks before sacrificing: diagonal clear, knight reaches g5, queen route to h5, and nothing defending g5 or covering f6.
One defender in the right place turns a winning sacrifice into a lost piece.
A pawn on e5 is an attacking piece — it denies f6 to every defender that wants it.
Source: Greek gift sacrifice — https://en.wikipedia.org/wiki/Greek_gift_sacrifice