Trap: 5.c5 dxe5 6.dxe5?

Against 5.c5 Black counterattacks with ...dxe5: if White recaptures on e5, the queen trade with check and ...N6d7 win a pawn.

1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.c4 Nb6 5.c5 dxe5 6.dxe5 Qxd1+ 7.Kxd1 N6d7

Move by move

1.e4 – White occupies the centre and opens diagonals for the queen and the f1-bishop.
1...Nf6 – The Alekhine Defence: the knight attacks e4 and invites the pawn forward, planning to attack the advanced white pawns later.
2.e5 – White accepts the challenge: the pawn chases the knight and gains space.
2...Nd5 – The knight centralises on d5, from where it eyes c3, b4, e3 and f4.
3.d4 – White adds a second pawn to the centre and supports e5.
3...d6 – Black immediately attacks the e5 spearhead: the typical way to challenge White’s centre.
4.c4 – The pawn chases the d5-knight and gains more space: White builds a big centre.
4...Nb6 – The knight retreats to b6, from where it presses on c4 and d5.
5.c5 – White chases the b6-knight again, but the c5-pawn moves away from the protection of the other pawns.
5...dxe5 – Black does not retreat the knight and counterattacks: now the d8-queen eyes d4 down the open d-file.
6.dxe5 – A mistake: recapturing on e5 opens the d-file and allows the queen trade with check.
6...Qxd1+ – Black trades queens with check: the white king must recapture and loses the right to castle.
7.Kxd1 – The king recaptures on d1: the b6-knight is attacked by c5, but Black has an answer ready.
7...N6d7 – The b6-knight escapes to d7 and attacks both c5 and e5: White cannot defend both and loses a pawn.

Black is about to win a pawn: the d7-knight attacks c5 and e5, and the white king on d1 has lost castling.

If White defends e5 (f4), capture on c5; if he defends c5 (Be3 or b4), capture on e5.
In the queenless ending develop quickly with ...e6, ...Bxc5 or ...Nc6 and bring the king to the centre.
The trap works because 6.dxe5 opens the d-file: White had to play 6.cxb6 and accept complications.

After 5...dxe5 Black’s queen eyes d4 and d1 down the d-file.