I find Na5 a good resource for black in this line of the french, profiting from the fact that white's b-pawn is binned to the bishop. As far as I can understand this position with my limited chess, I find it a strong move, winning space on queenside with the plan of trying Bd7-Rc8-Nc4 on c-file.

[FEN "r1b1kbnr/pp3ppp/1qn1p3/2ppP3/3P4/2P2N2/PP3PPP/RNBQKB1R w KQkq - 3 6"]

6. a3 Nh6 7. b4 cxd4 8. cxd4 Nf5
9. Bb2 Na5

However, I don't find this move at the database of chesstempo I use to use for my correspondence games.

chesstempo database before Na5

Stockfish neither considers it. It even don't play 10....Nbd2 (it plays Nc3) to defend on c4 (which I would expect), and doesn't wonder at all about Nc4 (it simply trades his bishop for the knight; apparently it should result an advantage on the center).

What's my misunderstanding here?

  • 1
    Strictly speaking, the pawn on b4 is the pinned piece (pinned to the bishop). – Brandon_J Jun 8 at 12:20
  • @Brandon_J true. thanks for the clarification and the edition. – Universal_learner Jun 8 at 12:24

The plan you outlined with ...Bd7, ...Rc8, ...Nc4 is a good strategical plan, but there are a few concrete reasons it doesn't work well:

  • In the opening you should be focusing on developing all your pieces and castling. Your plan with maneuvering the knight to c4 will move the same piece three times.
  • At depth 33, Stockfish gives 10.Nc3 Bd7 11.Rb1!, breaking the pin on the b2-bishop and attacking the a5-knight. Now you have to move the knight before your a8-rook manages to reach c8. If you go ahead with 11...Nc4 then 12.Bxc4 dxc4 is poor for you. Your new pawn on c4 is mainly a weakness at the moment, and White may blast open the centre with d5 to attack your uncasted king.
  • Also, White could always play 10.Qa4+. If you block with 10...Bd7 then 11.Qxa5 wins the knight. So you have to respond with retreating the knight: 10...Nc6.
  • I suspected the rupture of the center could cause troubles and didn't realized there was Qa4 – Universal_learner Jun 9 at 17:41
  • I learned that resource on the club some years ago, but I don't remember if it was on books. However the position where Na5 can be played profiting the undefeanded bishop on b2 should be sligthy different. – Universal_learner Jun 9 at 18:01
  • 1
    @Universal_learner Actually I just checked my reference DB and it turns out if you play 9...Bd7 and 10...Rc8 first, then 11...Na5 has been played a fair number of times (since you're basically two tempi ahead in your operation assuming White hasn't prepared to counter it). However, the problem is White could always play Nbd2 and then on ...Nc4 Nxc4 ...dxc4 you're still left with a pawn on c4 and White can blast open the centre with d5. In any case this might have been where you saw the idea. – Inertial Ignorance Jun 9 at 19:44

The Nbd2 --> Nc4 plan to protect the bishop doesn't work because c4 is attacked by black's pawn. Stockfish takes a more direct route to kick the pin:

[fen "r1b1kb1r/pp3ppp/1q2p3/n2pPn2/1P1P4/P4N2/1B3PPP/RN1QKB1R w KQkq - 0 1"]

1. Nc3 {White can kick the pin in a moment.} (1. Nbd2 {This move also poorly develops the knight - and as you can see, c4 is covered anyway.}) 1...Bd7 2. Na4

And the pin is already gone. Na5 didn't really do anything in the first place. It was interesting while it lasted, but that wasn't long. It wasn't exactly a bad move, even (lichess would call it an "inaccuracy," I'd wager); however, there are better ideas here, such as the simple developing move Bd7.

  • I meant with my poor english Nbd2 to prevent blacks Nc4. However stockfish doesn't worry at all about what I suposed a little hole and if black's knigth goes to c4 it simply trades it for his f1 bishop (on the Nc3 line), not wondering neither about the passed pawn generated on c4. – Universal_learner Jun 8 at 13:09
  • 1
    @Universal_learner Yeah, Nc4 by black could end up being a liability. It would indeed produce a passed pawn, but for practical purposes, an isolated passed pawn. Besides, if black wants any chance at controlling the c-file, why put a pawn on it?, etc. Solid thinking on your part, but not Stockfish-perfect thinking - and no one can reach that, anyway, so don't feel bad. – Brandon_J Jun 8 at 13:12
  • Maybe the problem is queen's position don't allows b5 to support the passed pawn. As Nc4 isn't a choise it is a move that migth finish with loosing some tempo after knigth's return to c6 – Universal_learner Jun 8 at 17:01
  • Absolutely@Universal_learner – Brandon_J Jun 8 at 17:29

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