The trapped knight on a5: a trap after 1.e4 e5 2.Nf3 Nc6 3.d4 d6

Against 3.d4, Black can protect e5 with 3...d6 instead of taking the pawn. Then 4.d5 attacks the knight on c6, and it needs a safe square. One natural choice loses it.

The line

1.e4 e5 2.Nf3 Nc6 3.d4 d6 4.d5.

The move: 4...Nce7

4...Nce7 brings the knight back towards the kingside, where it can go to g6. 4...Nb8 is also fine, and so is 4...Nb4, though after 5.c4 Na6 that knight is out of play. White keeps a little more space, but Black has a normal game.

The trap: 4...Na5??

The knight on a5 looks active, aiming at c4. But it's a dead end. b3 is covered by White's pawns, c4 by the bishop on f1, c6 by the pawn on d5, and b7 is Black's own pawn. 5.b4! attacks it, and it has nowhere to go.

Black gets a pawn back for the knight at best.

In rated online games in our library, 7% of players who reached this position played 4...Na5??

The idea to remember

Before you put a piece on the edge of the board, count its way back. A knight on a5 has only four squares to go to, and here White's pawns and bishop cover every one of them.

Train it

This is one of the opening traps OptiChess teaches as a play-through: the moves play themselves until the moment you need to look closely, then you find the move. The habit behind it, asking what your opponent can do after your move, is the blunder check.

Read more

• Why puzzles don't transfer to your games

More opening traps

• The Englund Gambit trap
• How to stop Scholar's Mate
• When Scholar's Mate fails
• The King's Gambit trap
• The Stafford Gambit trap
• Two Knights Defense, 4.Ng5 Nxe4
• The Scotch Game trap

Ways to train

• Chess tactics trainer
• Chess blunder trainer
• Chess pawn structures
• Chess endgame trainer
• Positional chess training
• Analyse your chess games