Fork
A fork is a move that leaves one of your pieces threatening two enemy pieces together. Because the opponent gets only one turn to respond, something usually falls.
In practice: before each move, look for a safe square from which one of your pieces would attack two targets at once, knights above all, because a knight attack cannot be blocked.
Also called: double attack by one piece
Chess is played one move at a time, and a fork turns that rule against the defender. You threaten two things with a single move, the opponent can repair only one, and the other is yours.
The geometry depends on the piece. A knight forks from a square that touches up to eight targets and cannot be blocked, which is why it is the usual hero. A rook forks along its rank and file, a bishop along two diagonals, and a queen can combine all four lines. Pawns fork too, because a pawn that steps forward may eye two squares at once.
Check makes any fork nastier. When one of the two targets is the king, the reply is forced and the second target is simply left alone. Even a fork of two knights is serious if the forking piece cannot be taken.
Finding forks is a habit of asking where each of your pieces could land and what it would hit from there, with special attention to enemy pieces that share a rank, file or diagonal with an empty square you can reach. Defending is the same exercise from the other side: before you park two valuable pieces a knight's jump or a line apart, check whether a single landing square touches both.
In the diagram White plays Re5. On the fifth rank the rook points at the knight on b5 and the knight on h5, and neither knight can capture it. Black can rescue only one, so White takes the other with Rxb5 or Rxh5.
Also worth reading is Decoy. A decoy is a tactic that lures an enemy piece onto a chosen square, usually with a sacrifice it has to accept, so that the piece can be forked, blocks one of its own lines or loses its old job.
Also worth reading is Desperado piece. A desperado is a doomed piece that cashes in before it dies: it captures or gives check, taking the most it can from the position instead of being lost for nothing.
A neighboring idea is Greek gift sacrifice. The Greek gift sacrifice is a bishop sacrifice on h7, or h2 for Black, played as Bxh7+ Kxh7, followed by a knight check on g5 and the queen coming to the h-file to attack the exposed king.
To see how often "Fork" or a pattern like it decides your own games, book a first lesson: George Li reviews your games and writes a study plan around what he finds.
Related terms
A knight fork is a move that places a knight on a square from which it attacks two or more enemy pieces at once, so the opponent cannot save them all.
A royal fork is a fork that attacks the enemy king and queen at the same time, most often with a knight, so the king must move and the queen is lost.
A pawn fork is a pawn move that attacks two enemy pieces at once, one on each of the two diagonal squares ahead of the pawn, so only one of them can escape.
A double attack is one move that creates two threats at once, whether they come from a single piece or from two, and whether they aim at pieces or at checkmate.
A pin ties a piece to its square: a bishop, rook or queen attacks it, and stepping aside would expose a more valuable piece standing behind it on the same line.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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