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Help understanding why move labeled blunder

  • #1

      I was black in the Icelandic(pretty sure that's what position is called). I am having a hard time seeing why my fifth move c5 was labeled a blunder.  I had to move my bishop for the second time but it wasn't anything that ruined my position or cost me material. I maybe lost some tempo but I really can't see how this is a blunder when I've seen moves that lead to getting checkmated only be labeled a mistake. Obviously my opponent did not capitalize on my blunder but usually when this happens I can see the move/moves he should have done to understand my blunder. In this case I really cannot. I think I played(for my skill level) pretty well the rest of the game. Thanks for any help/knowledge. 



  • #2
  • #3

    You played a gambit - you are down a pawn.  It should not be a surprise that if you don't play precisely you will just be down a pawn, and dropping a pawn is a blunder (anything that changes the evaluation by more than + or - 1.0 or more).  Here, after 5. ... c5 6. d4, the engine rates the position at -1.4, meaning slightly worse than down a pawn.  By contrast, after 5. ...bb4, which is "the move", there are some continuing tactics and black actually wins more than his share - black is doing fine and very much not just down a pawn.  After 5. ... c5 6. d4, white is up a clean passed pawn, black can no longer play bb4, and white gets another move as a bonus.  So the net is more than a pawn's worth of difference in the eval.  


    Only real take-away here is that you shouldn't play a gambit without *some* knowledge of opening theory.  For the most part anyway.  

  • #4

    @ArtNJ  Thanks for taking some time to respond. I sort of see what your are saying but I just don't see how bb4 is that good of a move. I thought about doing that move but to me it seems like it's just going to result in an exchange of bishops and allow him to activate his knight on the recapture. And after that what's to stop him from playing d5 anyway and kicking my bishop. If you don't mind could you elaborate on a continuing tactic that would win more than my share? Either way I appreciate the time.

  • #5

    Its pretty complicated because white has two logical responses (bd2 and nc3).  https://www.365chess.com/opening.php?m=11&n=18527&ms=e4.d5.exd5.Nf6.c4.e6.dxe6.Bxe6.d4.Bb4&ns=  In general, black gets fast development, and there are tactics in certain lines that allow more pressure.  For example, if 6. nc3 ne4! and what does white play that both defends the pinned knight and holds the dpawn?  


    Look its complicated stuff.  Its not like the queen's gambit where you can do a quick playthrough, maybe with a tad of help, and see once and forever that trying to hold the gambit pawn doesn't work out well for white.  You are going to have to play through the various lines in the link above and take some time if you want to understand how things shake out.  However, it is comparatively easy to see that with the option you chose, white is just winning, with a passed extra pawn being much more important than a now tiny temporary lead in development.  


    Gambits are persnickety, since if you don't play just so, the other side will catch up in development and you'll be just down a pawn.  There is often only one or two moves that are serious tries to get compensation.  So you have to learn the lines a bit - or avoid them.  

  • #6

    As Art says, you cannot afford to lose time or make inaccuracies if you gambit a pawn. You should usually look to get your compensation with piece activity and quick development. Here after Bb4+ Bd2 there is Qe7. This defends the bishop and also threatens discovered check if you move the Be6. With this position black has compensation for the pawn in the superior development and immediate threats.

  • #7

    I have looked at the position and I cannot understand why c5 is a blunder there. Of course c5 is not the best move there. Bb4 sort of just jumps out as I see the position. Bb4 Bd7 Bxd7 Qxd7 Ne4 Qd6 Bf5 and its already a great attack for black. However c5 is not a blunder. A mistake for sure, but a blunder is probably too harsh an assesment by the engine.

  • #8

    In your line Jayesh (i presume you meant this) Bb4+ Bd2 Bxd2 Qxd2 Ne4 Qe3 is stronger than Qd3. This is also lining up with the king and black has a big problem eg.Bf5 f3 wins the knight. Or Nd6 d5 wins a piece. So f5 is forced and its a mess for black, down a pawn, no attack and probably still losing a piece. Im not sure how the engine determines what is a blunder vs an inaccuracy or a mistake but c5 then d5 from white just leaves white a full passed pawn up with no compensation for black. The engine will almost certainly win from such a position so i guess this is why it classes it as a blunder.

  • #9

    Look at it this way: if you lose a pawn for nothing, that's a blunder, right?  Not as bad as losing your Queen, but still a blunder.

    When you play a gambit, you give up a pawn for some compensation, usually open lines, faster development and attacking chances.  If you make a move that limits your attacking chances or closes lines, then you have no compensation.  It's the same as just losing a pawn for nothing.

    One thing to realize with computers, not all blunders are created equal.  You may have a winning tactical shot, but you don't see it and play something else.  Your move doesn't lose, but you 'lost' the ability to win a Queen, say, so it's still a blunder (a blunder of missed opportunity, so to speak).  Similarly, playing c5 doesn't 'lose' any material, but you are already down a pawn and you now have fewer attacking options, and so it's a mistake in this sense.

  • #10

    Black's main idea in this gambit is to pressure white's pawns(c4 and d5).

    5...c5 allows white to advance his pawn and all compensation Black had is lost.Black has no pressure , he is a pawn down and in the resulting closed position his lead in development is close to useless.

    5...Bb4+ on the other hand ,initiates a pressure that is very unpleasant for white.

    Here is an example:


  • #11

    One more example that shows how unpleasant Black's pressure is

    I think you understand now that 5...c5 is a move that helps white and doesn't belong in this position.It's not an exaggeration to call it a blunder.

  • #12

    @Strangemover, yes I had gotten the ranks mixed up. However you got the point across and yes Qe3 is a big problem. Saw the Qe3 after I had posted that post, and the whole line is almost refuted after Qe3. That knight would be nearly trapped. After f3 black is lost.


    So ofcourse Bf5 won't be played if Qe3. But then the whole line sort of loses plot after that. I am sure there is a better line of moves for black. I can't quite find it though.



  • #13

    I think the simple answer is that if the computer evaluates you move as inferior to its best move by more that an arbitrary amount, it calls your move a blunder. In the case of your 5...c5, my computer evaluates the position after its choice, 5...Bb4+ at (+0.01), or essentially equal. After your 5...c5, it evaluates the position at (+1.33). In other words, you are down a pawn with less than no compensation. I suppose you call that a blunder, but I would have you move an inaccuracy.

  • #14

     One thing you learn from these computers is tactical vision. They may not be the best at deep positional play, but they are monsters at sharp tactics. They don't miss anything when it comes to direct tactical shots. That's why it considered 5,,c5 a blunder, it took all the tactical opportunities away from you.

  • #15

    If 5...c5 has to be labeled a blunder, it is for strategic reasons.  As a gambit player, you are trading a pawn for tension in the center. By allowing white to play 6 d4, you have given him an opportunity to release that tension and you are a pawn down. You have also given white a protected passed pawn. If you can't conjure up any counterplay, you will be in a lost ending. White will try to simplify by trading pieces, so as to enter a won endgame. As the endgame approaches, that protected passed pawn will become more and more important. Why? Black's king will be tied to that pawn to prevent it from promoting. In the meantime, white's king will be free to roam the board, gobbling up pawns. That could be the case, even if you weren't down a pawn.


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