Indian Defense: Accelerated London System: what should Black play?

In the Indian Defense: Accelerated London System, the position after e3 h5 Bg3 presents Black with a critical decision regarding the tension on the g3 square. The most effective and statistically dominant continuation for Black is Nxg3, which is played in 89.3% of the 54,389 recorded games at this position. This move aims to secure the bishop pair and disrupt White's kingside structure, maintaining a nearly equal engine evaluation of -0.10.

The strategic objective of Nxg3

The primary goal of Nxg3 is to eliminate White's influential dark-squared bishop, which is a cornerstone of the London System's defensive and offensive setup. By forcing the exchange, Black ensures that White must accept a doubled pawn structure on the g-file or h-file. According to the main line Nxg3 hxg3 g6 c4 e6 Nc3, Black typically follows up with g6 to prepare a solid kingside fianchetto or central development, neutralizing White's typical attacking patterns.

White's response and scoring

Despite the loss of the bishop pair, White maintains a competitive scoring rate of 55.1% after Nxg3. This is largely due to the opening of the h-file, which can provide White with semi-open file pressure if Black castles kingside prematurely. The engine evaluation remains close to parity, suggesting that while Black achieves a long-term structural advantage, White retains sufficient activity and central control to complicate the middlegame.

Alternative continuations and risks

Other moves are significantly less common and generally less favorable for Black. The move g6 is the second most popular choice, appearing in 3.1% of games with an evaluation of +0.14, leading to the line g6 Bh4 Ng7 c4 Nf5 Bg5. Retreating the knight with Nf6 allows White a comfortable advantage of +0.79. More experimental tries such as Bf5 or c6 are considered major inaccuracies, with engine evaluations exceeding +4.10, as they often allow White to capture the hanging knight on h5 via Qxh5.