Play on both flanks is a strategic concept that involves creating threats on both the kingside and the queenside, forcing the opponent to spread their defensive resources across the entire board.
The core idea is straightforward: no player can defend two fronts at full strength simultaneously. By launching pressure on the queenside — for instance by advancing pawns to open files — and then switching the attack to the kingside once the opponent rushes pieces over to defend, you stretch their position to its breaking point. This approach is typically employed by the side holding a positional or material advantage, with the goal of inducing weaknesses rather than forcing a direct breakthrough.
In practice, play on both flanks is especially powerful in endgames and middlegames where the opponent has built a solid but passive setup. Instead of hammering away at a well-defended position on one side, create a diversion on the opposite flank to pull defending pieces away, then exploit the imbalance that follows.