Queen's Indian Defense, Kasparov Variation

The Kasparov Variation is defined by developing White’s b1-knight to c3. In algebraic notation, N means knight, so 4.Nc3 names the piece and its destination square. From c3 the knight controls d5 and e4 and helps build a broad center. The move is natural and efficient, but it allows Bb4: Black’s bishop may go to b4 and pin the knight to the king. A pinned piece can move legally only if doing so does not expose its king to check, so its freedom is restricted.

Black is not required to play ...Bb4. Black may also fianchetto with ...Bb7, pressure e4, and prepare ...d5 or ...c5. If the bishop goes to b4, the game may acquire Nimzo-Indian features, although White's g1-knight is already on f3 and that difference changes many lines. This is called a transposition: different move orders reach the same or a closely related position.

White's choice

With Nc3, White values development and central control more than prevention. White may continue with Bg5, e3, Qc2, or a3 depending on the black bishop's placement. The most ambitious plan often includes e4, but it works only if the pieces can support the center and pressure on c3 creates no tactic.

The Petrosian Variation reverses the priorities: a3 prevents ...Bb4 before the knight develops. The Kasparov saves that tempo but accepts more immediate pressure on c3.