3...Nf6 4.d4 exd4 5.e5: the knight on d5 is variation 2 of 6 in the Ponziani Opening course, a beginner opening course for White (ECO C44). It runs 19 moves and begins 1. e4 e5 2. Nf3 Nc6 3. c3 Nf6 4. d4 exd4 …. Black takes on d4 and White kicks the f6 knight with 5.e5. White takes back with the c-pawn, trades the dark-squared bishops and castles. The pawns on d4 and e5 give White more space. In the lesson every move is explained on a board and then drilled; it is free.
Move by move
1. e4 – White takes the centre.
1... e5 – Black claims an equal share.
2. Nf3 – White develops and attacks e5.
2... Nc6 – Black defends e5.
3. c3 – The Ponziani. White prepares d4.
3... Nf6 – The Jaenisch Counterattack. The knight attacks e4.
4. d4 – White strikes in the centre at once.
4... exd4 – Black takes the pawn. This is Black's most common reply.
5. e5 – White kicks the f6 knight and gains space.
5... Nd5 – The best square. The knight stands well in the centre.
6. cxd4 – White takes back and now has two strong pawns in the centre.
6... Bb4+ – Black checks and offers to trade the dark-squared bishops.
7. Bd2 – White blocks the check and offers the trade.
7... Bxd2+ – Black trades the bishops.
8. Nbxd2 – White takes back with the knight and develops a new piece.
8... d6 – Black attacks the e5 pawn and opens the c8 bishop.
The lesson goes on for 3 more moves, each with its explanation.
chessGM