King's Gambit Accepted, Muzio Gambit

Coordinates in algebraic notation combine a column letter and a row number; g4 is column g, row four. The Muzio Gambit appears after Black accepts the f-pawn and advances a pawn to g4 to attack White's knight. Instead of moving the knight, White uses castling, the special move that moves the king and one rook at the same time. This places the rook on the f-file, the vertical line formed by squares with the letter f, and accepts that the knight may be captured.

What White receives for the sacrifice

• A lead in development, because several white pieces can enter the game before Black finishes organizing.
• Open lines for the queen, the bishop on c4, and the rook on f1, especially around f7.
• The initiative, meaning the ability to create threats that force the opponent to respond.

If Black captures the knight and White recaptures on f3 with the queen, White has given up a large amount of material. Material is the combined value of the pawns and pieces. The attack therefore needs concrete threats, not merely a dangerous appearance. If Black coordinates the pieces, protects the king, or returns some material to extinguish the attack, the remaining material advantage can decide the game.