Keene's Defense

Keene's Defense declines the King's Gambit with an immediate queen check along the e1–h4 diagonal that 2. f4 has just opened. The check exploits the loosened kingside directly instead of using the free tempo Black gains from the gambit. The usual answer, 3. g3, blocks the diagonal and attacks the queen, which must retreat. White's g-pawn advance also supports f4, and with the diagonal shut, fxe5 becomes a real threat rather than a tactical blunder. In return, Black can point to the light squares weakened around White's king. The main cost is time, because the queen has moved twice without improving Black's development.

Nearly every game continues 3. g3. The king walk 3. Ke2 is a rare alternative that gives up castling, and Black scores well against it. After 3. g3, the engine gives White a slight edge. In practice White wins somewhat more often than Black, and draws are uncommon, which fits an unbalanced, tactical opening played mostly at club level.