It is a positional reason. After c4 white can't take it, because b takes c4 and the white bishop is awful and white has problems on the b file. White can't go d4 because e4 is hanging. If white defends d3 with Qe2 then Rc8, then take on d3 and and Nc4. For the first sight...
Board Analysis - Pirc Defense - ~1600 ELO - Why does Stockfish recommend 12... c4 in this position?
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https://www.chess.com/club/analysis-with-cm-u2ro/join/1fc964
Ok but even line I was looking at 12 ...c4 13pxp Nxc4 14BxN pxB 15Nb-d2 is only a nice plus fpr black, and it's about the third best line according to software. White isn't being knocked out of the park after 12...c4, especially at 1600 level.
Stockfish doesn't know, that a 1600 is playing :)
I love nice plus :) Now I see that after b×c black can take e4 too, but I didn't check the softwer. What does it say, which is the best?
U2ro wrote:
I love nice plus :) Now I see that after b×c black can take e4 too, but I didn't check the softwer. What does it say, which is the best?
12...c4 13.dxc4 Nxe4 doesn't look right. After 14.cxb5 white is threatening Bd5.
Software thinks something like 12...c4 13Nb-d2 pxp 14Qb1 and a later Qxd3 is best, with a small advantage for black.
C5-C4 is a good move because it blocks the white bishop’s control of a2-a8 diagonal. If white plays dxc4 and black recaptures with bxc4, then the e4 pawn becomes weak and it results to opening of the b file for black to take advantage of (weak b2 pawn). Position is not lost for white though. White can play Nbd2 to protect e4 and attack c4 pawn at the same time and he can defend the b2 pawn with Rb1 when attacked. One drawback of black’s c4 move is that white can now occupy the d4 square with either the knight or the bishop. There’s still much play left for both players after c4.
While looking at Stockfish's analysis of a game, it found this position to be a critical turning point in which 12... c4 turned the tide of the game.
Can someone help explain the tactics and/or positional play that would help find this move?