The fast attack on f7
1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5
As early as the 16th century, the Italian chess master Giulio Cesare Polerio (1548-1612) analysed the continuation 3...Nf6, which virtually invites the white player to attack the Achilles' heel f7 with 4.Ng5. Although Siegbert Tarrasch (1862-1934) dogmatically branded this knight jump a "beginner's move", it has remained one of the main continuations against 3...Nf6 to this day. Hair-raising entanglements can arise as early as move four if Black simply ignores the threat against the f7-pawn and cold-bloodedly plays 4...Bc5, the Traxler Variation.
5.Nxf7 leads to 5...Nxf2+ and chaos, 5.Nxf7+ is considered the better continuation. But one thing is clear in both cases: anyone who plays like this without sufficient theoretical preparation is in for a rough time.
However, the main continuation for Black is 4... d5, which blocks the a2-g8 diagonal after 5.exd5.
Anyone who thinks they can now easily take the pawn with 5...Nxd5?! is mistaken. After the subtle 6.d4, which threatens the capture 8.Nxf7 after 6...exd4 7.0-0, Black has problems. There's also the brutal 6.Nxf7 - the Fegatello Variation - which leads to wild, deeply analysed complications after 6...Kxf7 7.Qf3+ Ke6. Better attempts for Black on the fifth move are the surprising 5...b5 (Ulvestad Variation) or 5...Nd4 (Fritz Variation), but the clear main variation is 5...Na5, which puts the knight on the edge but gains an important tempo by attacking the c4-bishop.
After 6.Bb5+ Black usually interposes the pawn with 6...c6, which leads to a gambit after 7.dxc6 bxc6 8.Be2 h6 9.Nf3 e4 10.Ne5 Bd6:
For the pawn Black gets a very active piece play.
Recently the retreat 8.Bd3 (instead of 8.Be2) has become established as the main continuation for White:
White's idea is to move his knight to e4 after 8...h6. The theory of this variation has developed considerably in recent years.
The Two Knights Defence (or Two Knights Game) after 4.Ng5 is a tactical minefield, dangerous for anyone who enters it. Attack and counter-attack determine the game early on. Both players must be wide awake! Anyone who likes to play actively with Black and is not afraid of sacrifices will love this opening.