Two Knights Defense: Traxler & Knight Sacrifice

Two Knights Defense

Definition

The Two Knights Defense is a double-king-pawn opening that arises after the moves 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6. Black’s third move develops the king’s knight aggressively, immediately attacking the e4-pawn and inviting sharp play instead of the quieter Giuoco Piano (3…Bc5). The ECO codes most commonly associated with the opening are C55–C59.

Strategic Themes

Dynamic Imbalance: Black forgoes the harmonious Bc5 setup and accepts structural risks to create tactical counter-chances.
Central Tension: The pawn on e5 is often a target; White must decide whether to defend it calmly (4.d3) or attack immediately (4.Ng5).
King Safety: Both sides usually delay castling until the central fireworks have resolved. The side that misjudges the tactics can see its king mated quickly.

Main Continuations

4.d3 — The Modern/Anti-Knight line, aiming for a solid center.
4.Ng5 — The celebrated Knight Sacrifice Line (see third definition below), leading to wild positions where material is often secondary to initiative.
4.Nc3 — The Italian Four Knights hybrid, usually transposing to quieter waters.

Historical Significance

The opening has attracted attacking geniuses from the Romantic era—Paul Morphy, Adolf Anderssen, and later Rudolf Spielmann—through to modern tactical specialists like Hikaru Nakamura. Its fashionable peaks often coincide with advances in opening theory and analytical tools; modern engines still uncover novelties in positions first explored in the 19th century.

Illustrative Game

Morphy vs. Anderssen, Paris 1858—perhaps the most famous Two Knights skirmish. Morphy’s intuitive sacrifices produced a brilliant mating net:

Interesting Facts

The name “Two Knights” refers only to Black’s development; White’s knights may already or eventually join the fray, but the opening is defined by Black’s …Nc6 and …Nf6.
In 2015, the line saw a renaissance at elite level when Caruana and Nakamura used it to score crucial wins in the Grand Chess Tour.
The opening is a common feature in puzzle books because many themes—double check, smothered mate, and discovered attack—appear naturally.

Traxler Counterattack

Definition

The Traxler Counterattack (also called the Wilkes-Barre Variation) is the audacious reply 4…Bc5!? to the Two Knights Defense after 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5. Instead of defending the vulnerable f7-square, Black counter-sacrifices on f2 or g1, leading to razor-sharp, almost forced complications.

Typical Move Order

1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 Bc5!?

Strategic & Tactical Ideas

Mutual King Hunts: Each side ignores threats to its own king in order to attack the opponent’s. Precision is paramount.
Piece Activity over Material: Material imbalances of +/- a rook are common; time and open lines decide the game.
Forced Theory: Modern engine lines run 20–25 moves deep; one misstep is usually fatal.

Canonical Variations

5.Bxf7+ Ke7 6.Bb3 — The King Walk line where the black monarch roams to e7 and sometimes even g6.
5.Nxf7 Bxf2+ 6.Kxf2 — Leads to asymmetric material imbalances (usually two minor pieces for a rook and pawn).
Declined with 5.d4 — White can bail out into quieter waters, but even here tactics abound.

Historical Anecdote

The opening is named after Karel Traxler (Czechoslovakia, 1866-1936), a Catholic priest and problem composer who introduced the move in 1890. It later gained the alternative name “Wilkes-Barre” because American enthusiasts in Wilkes-Barre, Pennsylvania, analyzed it extensively in the 1920s.

Model Game

Marshall vs. Levitsky, Ostend 1907 — A spectacular showcase of Traxler tactics concluded in only 23 moves:

Interesting Facts

Some grandmasters, including Alexei Shirov and Baadur Jobava, still deploy the Traxler as a surprise weapon, trusting their memory over the opponent’s.
The line has been used in correspondence chess and computer engine vs. engine matches as a test-bed for calculation depth.
Statistically, practical results are close to 50-50, underscoring the opening’s double-edged character.

Knight Sacrifice Line

Definition

The phrase “Knight Sacrifice Line” most commonly refers to the variation 4.Ng5 in the Two Knights Defense, where White is prepared to sacrifice the knight on f7 for rapid development and a direct assault on Black’s king. The critical moves are:

1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Na5 6.Bb5+

Tactical Motifs

Fork on f7: The immediate threat is Nxf7, forking queen and rook.
Discovered Checks: After the sacrifice, White often obtains double checks such as Qf3+ or Bxd5+.
Open e- and f-files: The removal of Black’s f-pawn exposes the king to rook lifts and queen infiltrations.

Typical Continuations

5…Na5 — The main line, chasing the c4 bishop and forcing 6.Bb5+. Play can continue 6…c6 7.dxc6 bxc6 8.Qf3!.
5…Nxd5?! — The Fried Liver Attack; Black grabs the pawn but may succumb after 6.Nxf7 Kxf7 7.Qf3+.
5…b5?! — The Polerio defense, another offbeat yet dangerous try.

Historical Significance

During the 19th-century Romantic era the line epitomized the spirit of speculative sacrifice. Players like Louis Paulsen and Adolf Anderssen turned it into a battleground for attacking ideas. Today it remains a favorite in scholastic events because it teaches calculation, king safety, and the value of development.

Famous Example

Kieseritzky vs. Schallopp, Leipzig 1877 — a textbook execution of the knight sac:

Practical Advice

Before playing Ng5, make sure you know at least one concrete line; the theory is tactical and unforgiving.
If you are Black and wish to avoid the sac, consider 3…Bc5 (Giuoco Piano) or the Petroff Defense.
In blitz and rapid chess the Knight Sacrifice Line scores disproportionately well because it tests an opponent’s defensive precision early.

Interesting Facts

The moniker “Fried Liver” comes from the Italian expression fegatello, suggesting Black’s position is “dead meat” after 5…Nxd5? 6.Nxf7.
Modern engines show that with best play Black can survive, but only via narrow paths such as the 5…Na5 main line.
In 2021, teenage prodigy Praggnanandhaa defeated several GMs online using the knight sacrifice—even though the line is nearly 170 years old.