Two Knights Defense, Modern Bishop's Opening

The Modern Bishop's Opening is White's restrained answer to the Two Knights Defense. Rather than testing Black at once with 4. Ng5 or opening the center with 4. d4, White simply supports the e4-pawn with 4. d3. The move gives up any immediate pressure on f7 and any pawn sacrifice, frees the c1-bishop, and leaves the central break for later. Setups built on an early d2–d3 are often called the Slow Italian, and once Black answers with ...Bc5 the position becomes the Giuoco Pianissimo. It is the most frequently chosen fourth move against the Two Knights.

The play is about maneuvering rather than early contact. White usually adds c3, castles, posts a rook on e1 and develops the queen's knight via d2, keeping d3–d4 in reserve as the main central break. The light-squared bishop often drops back to b3 and later c2, giving the game a Ruy Lopez character. Black commonly answers with ...d6 combined with ...a6 or ...a5, or castles first and prepares ...d5 to open the position.

Nearly half of all games continue 4...Bc5, the Giuoco Pianissimo; after 5. c3 this reaches the modern main line of the Italian, a frequent guest in top-level play this century, where the wealth of plans and move orders limits the value of computer preparation. 4...Be7 is a more modest setup that keeps the bishop out of the way of a later d4 and leaves Black free to choose between ...d6 and ...d5. 4...h6 rules out both Ng5 and the Bg5 pin before Black commits. 4...d5 strikes in the center at once and leads to a more open game than the other replies. The engine's preferences are 4...Bc5, 4...a6 and 4...h6.

The d3 systems helped revive the Italian in the late 20th century, when Karpov used the Giuoco Pianissimo in his 1981 world championship match, and they became a standard alternative to 3. Bb5 once the Berlin Defense grew popular after the Kramnik–Kasparov match of 2000. In online games White scores slightly better and draws are rare, while the engine judges the position roughly balanced.