Lesson
White to move. Main line: 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Nxd5 6. Nxf7 Kxf7 7. Qf3+ Ke6 8. Nc3
The knight sacrifice works because 6...Kxf7 is nearly forced (declining leaves White a pawn up with the initiative) and 7.Qf3+ hits both the king and the pinned knight on d5. The miserable 7...Ke6 is the only way to keep the extra piece — the king personally defends d5.
After 8.Nc3 White piles onto the pinned knight with a raging attack; engines hold the line for Black with only-moves, but over the board the defense is close to impossible below master level.
The practical lesson sits at move five: 5...Nxd5 is the natural move and the losing one. 5...Na5, hitting the c4 bishop, is why club players should know this line from both sides — one move-order detail decides whether Black is fighting for equality or for survival.
The safe path (avoiding it all): 5... Na5 — the main-line antidote: Black gambits a pawn instead of allowing Nxf7.
A knight for the king’s safety
White sacrifices a knight on f7 to pull the black king to a square where it can be attacked and cannot easily return. The king ends up on e6 — in the centre, on move six, with pieces still undeveloped.
It is the sharpest way to punish 5...Nxd5, and it is the reason that recapture has a reputation.
How good is it really?
Engine analysis is more measured than the reputation. After the sacrifice White is around +0.7 — clearly better, with an ongoing initiative, but not winning by force. Black is not lost; Black is uncomfortable, which is a different thing.
Practically that distinction rarely survives the clock. Defending an exposed king with no development is hard, and the position is far easier to play from White’s side.
The line that avoids all of it
Black does not have to allow this. The recommended answer is ...Na5, attacking the bishop instead of recapturing on d5, and it removes the entire attack at the cost of some structural concessions.
This is the useful takeaway for an opening trap: the antidote is usually one move, and knowing it is worth more than knowing the trap.
6.Nxf7 (the sacrifice): About +0.7. A strong practical try; the quiet 6.d4 evaluates fractionally higher.
5...Nxd5 (allowing it): The recapture that walks into the attack — playable, but this is the line to know before choosing it.
...Na5 (the antidote): Sidesteps the sacrifice entirely by hitting the bishop first.
A sacrifice that exposes a king buys time, and time is what an undeveloped defender lacks.
“Winning” and “much easier to play” are different claims; most opening traps are the second.
Learn the antidote to any trap you learn — it is usually a single move.
Source: Fried Liver Attack — https://en.wikipedia.org/wiki/Fried_Liver_Attack