Russian IM Mark Dvoretsky is one the most respected chess trainers in the world today.

In his March 2015

Unjustified Weakening of the Pawn Structure

As a rule, White strives to exploit his opponent's kingside weaknesses by playing for attack, and keeping the queens on
the board. But sometimes, pawn structure minuses make themselves felt even deep into the endgame, as the following
examples demonstrate.

Tal - Korchnoi

Game 1, Semi-Final Candidates' Match, Moscow 1968

1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb7 5.Bg2 Be7 6.0-0 0-0 7.Nc3 Ne4 8.Qc2 Nxc3 9.Qxc3 c5 10.Be3(10.Rd1) 10...Bf6

10...d6 is considered more exact. White could meet the text move by 11.Qd3(d2), to prevent the exchanging operation
that follows.

11.Rfd1?! Bxf3 12.Bxf3 Nc6 13.Bxc6 dc 14.Qd3 cd 15.Bxd4 c5 16.Bc3(16.Bxf6 Qxf6=) 16...Qe7 17.Qd7 Rfd8
18.Qxe7 Bxe7 19.e4

[FEN "r2r2k1/p3bppp/1p2p3/2p5/2P1P3/2B3P1/PP3P1P/R2R2K1 b - - 0 19"]

1...?

The position is held without much difficulty hadBlack played 19...f6 andKf7-e8.

19...h5?!20.Kf1 Bf6?(20...f6) 21.Bxf6 gf

The unjustified weakening of his pawn structure immediately put Viktor Korchnoi on the verge of losing.

22.Ke2 Kg7 23.Rxd8! Rxd8 24.Rd1! Rxd1

The attempt to activate his rook on the b-file, by 24...Rb8 25.Rd7 b5, would be parried by 26.Kd3! bc+ 27.Kc3+/-.

25.Kxd1 Kg6 26.Ke2 Kg5 (26...f5 deserves attention) 27.Kf3

It is important not to allow the king on g4. 27.h3, with the same idea, would be weaker, in view of 27...f5.
27...f5

White intends 28.h4+, followed by Kf4, f2-f3, and g3-g4, creating an outside passed h-pawn.

[FEN "8/p4p2/1p2p3/2p2pkp/2P1P3/5KP1/PP3P1P/8 w - - 0 28"]

1.?

The game wound up as follows: 28.h3?! Kf6(28...e5 leads to approximately the same thing) 29.Kf4 e5+ 30.Ke3 a6
31.b3 Ke6 32.ef+ Kxf5 33.f3 Ke6 34.g4 f5!(it's important to prevent 35.Ke4; 34...hg? 35. fg!+- would be a terrible
mistake) 35.gf+

On35.ghKf6 36.Kf2 Black holds his position by36...Kg7! (but not36...Kg5? 37.f4+!) 37.Kg3 Kh7! (a mistake would
be37...b5? 38.Kh4! Kh6 39.a3, as Black falls into zugzwang) 38.a3 Kh6 39.Kh4 b5 - here, it's White who gets into
zugzwang.

35...Kxf5 36.h4 Kf6 37.Ke4 Ke6 38.a3 b5 39.cb ab 40.Kd3(40.a4 c4!) 40...Kd6Drawn.

I have analyzed what would have happened, had Mikhail Tal played31.a3!? (instead of31.b3). In that case, the defensive
method Black used in the game would have lost: 31...Ke6 32.ef+ Kxf5 33.f3

[FEN "8/5p2/pp6/2p1pk1p/2P5/P3KPPP/1P6/8 b - - 0 33"]

1...?

33...Ke6? 34.g4 f5 35.gh! Kf6 36.Kf2 Kg7 (36...Kg5 37.f4+!; 36...b5 37.Kg3 Kg5 38.f4+!) 37.Kg3 b5 (37...Kh7 38.Kh4
Kh6 39.a4 a5 40.b3+-) 38.Kh4! Kh6 39.b3when Black is in zugzwang.

The waiting move 33...f6! improves things for Black. 34.g4+ hg 35.fg+ Kg5, is not dangerous; and on 34.b3, White
loses a valuable tempo on the queenside.

However, the immediate clarification of matters on the queenside, with 33...b5!, is now playable as well.

A) 34.g4+ hg35.fg+ Kg5 36.b3 (36.cb? ab37.b3 even loses:37...b4! 38.ab cb 39.Ke4 f6 or 38.a4 c4 39.a5 cb 40.Kd2 e4
41.a6 b2 42.Kc2 e3 43.a7 e2-+) 36...bc 37.bc Kh4 38.Ke4 Kxh3! (weaker is38...f6 39.Kf5) 39.g5 Kg4 40.Kxe5 Kxg5
41.Kd5 f5 42.Kxc5 f4 43.Kd4=;

B) 34.cbab35.Kd3!? (more dangerous for Black than35.b3 Ke6 36.g4 h4!=) 35...Ke6 36.g4

[FEN "8/5p2/4k3/1pp1p2p/6P1/P2K1P1P/1P6/8 b - - 0 36"]

1...?

36...h4! 37.Ke4 c4! 38.g5 f5+ 39.gf Kxf6 40.f4 ef 41.Kxf4 Ke6 42.Kg4 Kd5 43.Kxh4 Kc5! (losing is43...Kd4? 44.Kg4
Kd3 45.h4 Kc2 46.h5 Kxb2 47.h6 c3 48.h7 c2 49.h8Q+ Kb1 50.Qh7 Kb2 51.Qg7+ Kb1 52.Qg6 Kb2 53.Qf6+ Kb1
54.Qf5) 44.Kg4 b4 45.ab+ Kxb4 46.h4 Kb3 47.h5 Kxb2 48.h6 c3 49.h7 c2 50.h8Q+ Kb1, and the queen cannot win
against a bishop's pawn, as is well known.

Now let's go back to the position after Black's 27th move. Yuri Averbakh writes:

V. Smyslov, S. Furman, and Y. Averbakh subjected this position to exhaustive analysis; and finally managed
to show that White could have won with 28.e5!

White's advantage here comes down to two main factors: he has the better pawn structure and a greater
number of pawn moves, which ought to play a decisive role in the battle for zugzwang.

With 28. e5, White starts a plan that is characteristic of such positions: he intends to drive away the king by
h2-h4; he will then occupy the f4-square with his own king and, advancing his pawns by f2-f3 and g3-g4,
create an outside passed pawn on the h-file.

I would not have repeated all this well-known (and, truly, already half-forgotten)
analysis, had I not come to the
opposite conclusion: despite the opinion of these respected grandmasters, Black could still save himself! Back in the
day, in my training sessions, more than once I offered strong players the opportunity to play out this position. And one
day, when entering the just-completed "game" into my computer, suddenly I discovered a hitherto unseen possibility.

But all in good time!

He cannot prevent the king from being driven away by 28...h4. Vassily Smyslov gives the following variation:29.h3 a6
30.a3 a5 31.a4 Kg6 32.Kf4 Kh5 33.b3 (zugzwang) 33...Kh6 34.g4 Kg6 35.gf+ ef36.f3+-with a decisive zugzwang, or
33...hg34.fgKg6 35.g4 fg36.Kxg4+-- the outside passed pawn determines the outcome.

29.h2-h4+ Kg5-g6 30.Kf3-f4 a7-a6!

After 30...Kf7? 31.f3 Kg6 32.a3 a6 33.a4! a5 34.b3 a basic position for this kind of endgame occurs: mutual zugzwang,
Black to move. His king has to abandon the g6-square, after which White creates an outside passed pawn:34...Kf7
35.g4! fg36.fgfe+ 37.Kxe5 hg38.Kf4+-.

[FEN "8/8/pp2ppk1/2p1Pp1p/2P2K1P/6P1/PP3P2/8 w - - 0 31"]

1.?

The direct31.f3? b5 32.cb(32.b3 b4) 32...ab33.a3 c4 would lead to the same zugzwang position - except with White to
move. With his king at g6, 34.g4? fe+ 35.Kxe5 fg36.fghg37.Kf4 Kh5-+ does not work.

31.a2-a3!

The extra tempo b2-b3 must remain in reserve, as indicated by the variation31...Kf7? 32.f3 (but not32.a4? Kg7! 33.f3
Kg6 and it is White who is in zugzwang) 32...Kg6 (32...b5 33.cbab34.g4 fg35.fgfe+ 36.Kxe5 hg37.Kf4+-) 33.a4 a5
34.b3, and this time, it's Black in zugzwang.

Black responds to31.b3?! with31...Kf7! (since31...b5? is refuted by32.cbab33.Ke3! fe34.a4+-or 33...b4 34.f4!
fe35.feKf7 36.Kd3+-). After 32.a3 Kg6 White can't play for a tempo anymore:33.a4 Kf7 34.f3 Kg6=; 33.f3 b5!=; 33.b4
Kf7 34.b5!? ab 35.cb fe+ 36.Kxe5 Ke7 37.a4 Kd7 38.f3 Kc7(e7) 39.Kf4 c4! 40.Ke3 e5 41.f4! Kd6!=.

More interesting is32.f3 Kg6 (32...b5? 33.g4+-) 33.a3 (33.a4 a5=) 33...b5! 34.cbab35.Ke3!? fe36.Kd3! (upon36.a4? c4
White stands on the verge of defeat - just as he does after36.Kd2? e4! 37.fefe).

[FEN "8/8/4p1k1/1pp1pp1p/7P/PP1K1PP1/8/8 b - - 0 36"]

A safe way to draw was offered by Vladimir Belov and Vladimir Potkin: 36...e4+! 37.fe e5! 38.ef+ Kxf5 39.a4 e4+
(39...c4+? 40.Kc3+-) 40.Kc2 ba 41.ba Kg4=.

Another possible way is36...Kf7 37.a4 ba(37...c4+? 38.Kc3 cb 39.ab!+-) 38.ba Ke7 39.a5 Kd6 40.a6 Kc7 41.a7 Kb7
42.g4! e4+! (but not42...fg? 43.fg hg 44.h5 c4+ 45.Ke2+-) 43.Ke3 c4! 44.gh c3 45.h6 (45.f4 e5) 45...f4+ 46.Kxe4 c2
47.h7 c1Q48.a8Q+ Kxa8 49.h8Q+ Kb7=.

31...b6-b5! 32.c4xb5 a6xb5 33.b2-b3!

White intends to create an outside passed pawn on the queenside, by playing a3-a4 at the right moment. This of course
requires him to take into account the counterstroke c5-c4.

33...f6xe5+! 34.Kf4-e3!!

Indicated by Smyslov. It's a draw after34.Kxe5? Kf7 35.a4 (35.b4 c4 36.Kd4 e5+ 37.Kc3 Ke6=) 35...c4 36.bc ba
37.Kd4 Kf6! 38.Kc3 (38.f4? a3 39.Kc3 e5!-+) 38...Ke5 39.Kb4 Kd4 40.c5.

[FEN "8/8/4p1k1/1pp1pp1p/7P/PP2K1P1/5P2/8 b - - 0 34"]

1...?

34...Kf6

The king tries to get into the square of the a-pawn - Averbakh. (He is responsible for the entire variation that follows.)
35.a4 ba(35...Ke7 36.ab Kd6 37.f3! Kc7 38.g4+-) 36.ba Ke7 37.Kd3 Kd6 38.Kc4 Kc6 39.a5 f4 40.gf(40.a6? fg 41.fg
e4) 40...ef 41.a6 f3!?

White's job would be simpler after41...e5 42.a7 Kb7 43.Kxc5 e4 44.Kd4.

42.a7 Kb7 43.Kxc5 Kxa7

[FEN "8/k7/4p3/2K4p/7P/5p2/5P2/8 w - - 0 44"]

Now, which pawn should the king go after? It would be a mistake to play44.Kd4?! Kb6 45.Ke3? (it's still not too late to
play 45.Ke5) 45...Kc5 46.Kxf3 Kd4 47.Kf4 e5+ 48.Kg5 Ke4 49.Kxh5 Kf3 50.Kg5 Kxf2 51.Kf5 Kf3! 52.Kxe5 Kg4= or
52.h5 e4=.

44.Kd6! Kb6 45.Kxe6 Kc7 46.Kf5 Kd6

The same question here: which pawn does he attack?

47.Kf4!

47.Kg5? throws away the win: 47...Ke5 48.Kxh5 Kf5 (zugzwang) 49.Kh6 Kg4 50.h5 Kh3 51.Kg5 Kg2 52.h6 Kxf2
53.h7 Kg2 54.h8Qf2.

47...Ke6 48.Kxf3 Kf5 49.Ke3! Kg4 50.f4 Kxh4 51.Kf3!+-

And now - that defensive improvement I promised. Go back to the position after White's 34th move:

34...f5-f4+!! 35.g3xf4

After 35.Kd2? fg! 36.fge4! 37.a4 c4! 38.a5 (forced), 38...cb transposes into a lost queen ending for White.

35...e5xf4+!

The tempting 35...Kf5?! is refuted by36.a4! ef+ 37.Kd3! (37.Kd2? ba 38.ba Ke4-+). For example,37...c4+ 38.Kc3,
or37...e5 38.a5! e4+ 39.Kd2 c4 40.bc b4 41.a6 b3 42.a7 e3+ 43.fe fe+ 44.Kxe3 b2 45.a8Qb1Q46.Qf3+, or37...ba 38.ba
Ke5 39.Kc4 Kd6 40.a5 Kc6 41.a6 e5 42.a7 Kb7 43.Kxc5 e4 44.Kd4 e3 45.fe f3 46.Kd3 Kxa7 47.e4.

36.Ke3xf4

36.Kd3 e5! 37.a4 c4+ 38.Kc3 e4 39.ab e3 40.fe f3= isn't dangerous.

36...Kg6-f6

[FEN "8/8/4pk2/1pp4p/5K1P/PP6/5P2/8 w - - 0 37"]

By returning his extra pawn, Black wins an important tempo, in order to bring his king over to the queen's wing.

37.Kf4-e4 Kf6-e7 38.a3-a4

On38.Kd3 Kd6 39.a4 Black could answer not only 39...c4+ 40.Kc3 cb, leading back into the main variation, but also
with39...Kc6 40.Ke4 Kb6 41.abKxb5 42.Ke5 Kb4 43.Kd6 Kxb3 44.Kxc5 Kc3 45.Kd6 Kd4 46.Kxe6 Ke4 47.Kf6 Kf4
48.Kg6 Kg4=.

38...c5-c4! 39.a4-a5 c4xb3 40.Ke4-d3 Ke7-d6 41.Kd3-c3 Kd6-c6!

Or41...Kd5!. The c5-square is "mined": after 41...Kc5? 42.Kxb3 Black gets into zugzwang, and loses.

42.Kc3xb3 Kc6-c5!

Now it's White who is in zugzwang. He cannot win, either by43.f3 e5, or43.Ka3 b4+ 44.Kb3 Kb5 45.a6 Kxa6 46.Kxb4
Kb6 47.Kc4 Kc6 48.Kd4 Kd6 49.Ke4 Ke7= (or 49...e5 50.Kf5 Kd5=).

43.f2-f4 Kc5-d6(d5)! 44.Kb3-b4 Kd6-c6

Again zugzwang.

45.a5-a6 Kc6-b6 46.a6-a7 Kb6xa7 47.Kb4xb5 Ka7-b7=

Thanks to accurate king maneuvers, Black has kept his pawn on e6, which allowed him to save himself.

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