Queen's Indian Defense: Kasparov-Petrosian Variation, Andersson Variation

This chess opening is a solid and flexible defense that leads to rich middlegame positions, often favored by players seeking a balance between solidity and counterplay.

The opening is a popular choice among players who prefer a solid and flexible setup with Black. It is named after the legendary World Champions Garry Kasparov and Tigran Petrosian, as well as the Swedish Grandmaster Ulf Andersson, who have all contributed to its development and popularization. The opening is characterized by Black's fianchetto of the light-squared bishop on b7, which aims to control the central e4 square and put pressure on White's pawn on d4.

White's a3 move is a key feature of this variation, preventing Black from playing an early Bb4, which could pin the knight on c3 and create problems for White. The knight maneuver Nf3-e4 is another important aspect of this opening, as it allows Black to challenge White's central pawn structure and potentially exchange off one of White's central pawns.

The resulting middlegame positions are often rich in strategic and tactical possibilities, with both sides having chances for active play. Black's pawn structure is usually solid and compact, making it difficult for White to create immediate threats. However, White often enjoys more space and central control, which can be used to generate attacking chances or to slowly improve the position.

Overall, this opening is a reliable and flexible choice for Black, offering a good balance between solidity and counterplay.