4

Click here for engine re position below

8/3r4/1kp2p1p/ppRp2pP/3PP1P1/3K1P2/PP6/8 w - - 0 1

From hanging pawns in The Principle of Two Weaknesses in the Endgame at 9:02 (the game is discussed from 0:00 until 12:20).

The way Rd8 is described makes me think Rd8 is some natural defensive move in a rook endgame that is already winning for white.

But according to engine:

  1. The position is actually about drawish after a3 (eval 0.2)
  2. But the next move is critical: It seems that the only move that holds the draw is a4 (eval 0.1 or 0.2).
  3. Meanwhile, the evaluation goes from 0.2 to 3.4 for (a3 and then) Rd8.

Thus, it seems like Rd8 cost black a drawn game rather than that Black didn't really have that much chance to draw(/win) from the start (of the endgame in the video).

What's going on?

Similar question: akiba rubinstein vs alexander alekhine 1911 rook endgame: the mistake here is Rxb5 right?

2
  • 1
    Please post the actual position you are refering to rather than links to a video.
    – Evargalo
    Aug 17, 2021 at 15:53
  • 2
    @Evargalo Actually I did post a link to lichess engine re the position but anyhoo I now edited post to include a visual of the position. Thanks for commenting.
    – BCLC
    Aug 17, 2021 at 16:01

1 Answer 1

6

The mystery is easily solved if you just follow a few alternatives with the engine. The point is simply that if White comes to b4, the Rc5 gets another protection. This means that after exd5 Rxd5, White can march on with Ke4 as c5 is no longer hanging, and his activity wins in the long end (autoplay again). And cxd5 instead will immediately lead to zugzwang, and dxe4 is obviously (?) bad in any case. Thus not Rd8 is the cause of (probable) loss, but not blocking b4 in time.

4
  • What do you mean by b4 (by white instead of a4 by black)? The engine seems to evaluate the following line as a draw like really a flat 0.0 instead of something like -0.3 or +0.7: 1. a3 a4 2. b4 axb3 3. exd5 Rxd5 4. Rxd5 cxd5 5. Kc3 Edit 1: Also same with this line 1. a3 a4 2. b4 axb3 3. exd5 cxd5 4. Kc3 Rc7 5. Rxc7 b2 6. Kxb2 Kxc7 Edit 2: wait are you talking about 1. a3 Rd8 2. b4?
    – BCLC
    Aug 18, 2021 at 7:54
  • 1
    Exactly. If Black does allow White b4 uncontested, he seems lost. If he plays a4 and can take e.p., he is saved. Aug 18, 2021 at 14:33
  • To clarify: Am I correct to think that the hanging pawns guy is wrong in saying Rd8 and that I am/the engine is correct in saying a4 instead? You talk of 'mystery is easily solved'. I mean the mystery to me is why the hanging pawns guy says Rd8. I think Rd8 is wrong.
    – BCLC
    Aug 18, 2021 at 21:38
  • 1
    Where is the mystery? I make errors, hanging pawns makes errors (I checked him out, he's not remotely at his announced GM target yet), the engine is always right :-) and Rd8 is exactly wrong if White can establish a Pb4 (e.g. 1.Rc2 Rd8 is OK for Black), including the position where you say Rd8 is wrong. Aug 19, 2021 at 8:39

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