I can understand Nimzowitsch's zeal for the topic of blockade. Such a difficult task! When a mass of pawns is marching toward your position, it is a threatening sight. They are slow, but cheap and thus able to chase away every piece that is standing in their way. Stopping them seems equally impossible as stopping a tsunami or a bush fire.
Still, there are techniques how to stop these little folks. Ninety-seven years after Nimzowitsch's classical work on the blockade, let us revisit the territory with more recent examples.
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First question you need to ask yourself is: "Where am I able to establish the blockade?"
In the following example Aronian was deliberating where should he establish the defensive line:
Vachier-Lagrave – Aronian, Grand Slam Final 2013, Black to move:
Aronian's task is crystal-clear. If he stops White's pawns, with the help of his own passed pawn he will win the game. But how should he stop them?
Well, the first thing to notice is the presence of opposite-coloured bishops. That means that any successful blockade should be established on the dark squares. On the light squares, White is as strong as Black. Therefore, Black should fight for the h4-d8 diagonal, the last diagonal long enough to establish a full blockade.
Also, Black is a rook up. And pieces are much quicker than pawns. Therefore, slow play might favour the pawn avalanche. Aronian needs to act now! He needs to use his pieces actively, before the pawns start rolling.
Black played 48…Bg7!, the only move leading to a winning position. White is forced to play 49.e6 (49.f6 Bxf6!) and after 49…Bf6 Black seems to have reached his goal. However, now the white king enters the stage:
50.Kg3 a5 51.h4 Rg8 52.g5
Is the blockade broken? No, claims Aronian, never! I will not give up a single square! He played the lovely (and only) 52…Kg7!!. Sacrificing his bishop for the key g-pawn, he retained the blockading square f6. After 53.gxf6 Kxf6+ White's pawns are safely blocked, and the a-pawn will decide the game.
Black won soon.
Here's the complete game:
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Four years later, the same opponents met again. And again, it was Aronian's task to stop the avalanche of the Frenchman:
Vachier-Lagrave – Aronian, FIDE World Cup 2017, Black to move:
Again, Vachier-Lagrave's pawns are very mobile. White can prepare all sorts of pawn breaks, and for Black it is extremely unpleasant to watch out for all of them. Therefore, Aronian correctly decides to limit the mobility of White's avalanche:
27…h5! 28.g5 Bg7
Now White has lost the possibility of playing the h4-h5 break… But he can still move his e- and f-pawns. That means Black must continue his restraining job.
29.Rf1 Qa7 30.Qe1
What to do now? Black should have been consistent. After 30…d5! 31.e5 c5 he would stop the avalanche successfully. Black plans to play …Qa7-d7, and the immediate 32.f5 does not work because of the weakness of the e5-pawn. After 32…gxf5 White's knight is stuck at f3, defending the pawn.
Please note: you can immobilise a pawn not only by blocking a square in front of it, but also by attacking a target defended by this pawn.
Instead, Aronian played the slow 30…c5?, after which he was unable to stop the f4-f5 break in the following fight, and lost.
Here's the complete game:
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Sometimes, restraining a pawn chain involves compromising it:
Conquest – Williams, British Championship, 2010, White to move:
White's pawn avalanche on the queenside is further advanced, but it is not really dangerous. Black's light-squared bishop controls an important blockading diagonal. In fact, it is White that has to solve the riddle how to stop the march of Black's central pawns.
It is surprising how quickly Conquest, a strong and experienced GM, succumbed under the pressure. The game lasted only ten more moves, in which Black's central pawns moved to d4 and e4 and White had to resign.
However, the diagrammed position is still equal. The continuation I like most is 26.f5!?. For the price of a pawn, White destroys the harmony of Black's pawn chain. Both 26…exf5 27.Nd4 and 26…gxf5 27.Nd4 lead to complicated positions, in which White's chances are not worse. Most importantly, he is not getting steamrolled any time soon.
Please, remember: As wounded soldiers slow down the entire army, doubled pawns restrict the mobility of the entire pawn chain.
Here's the complete game:
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The last example will be somewhat different. Instead of patiently blocking the opponent's pawn chain, Anand decided to untie the Gordian know of the position with a sword:
Anand-Leko, Tal Memorial, 2009, White to move:
White is a piece up, but the black pawn avalanche looks really threatening. Moreover, White's knight is a poor, restricted piece. In such a situation, a purely defensive approach would probably lead to a disaster. The pawns are simply too advanced to establish a successful blockade.
However, if the pawns are too advanced, there is a lot of space behind them for a quick SWAT squad! In fact, both the black king and the b7-bishop are serious tactical weaknesses.
Therefore, Anand played the paradoxical 22.Nxd4!, and after 22…cxd4 23.Re6 Leko faced surprisingly difficult problems. He chose 23…Bc8?! (According to recent theory, 23…Rf6 should keep approximate equality.), and after 24.Rg6+ Kh7 25.axb5 White had the upper hand.
Here's the complete game:
Again, something to remember: A pawn chain is only threatening from the front. Once you are behind it, it does not bother you a thing. Therefore, getting your pieces behind the pawn chain of your opponent might easily turn the tables.
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To sum the article up: There are three strategies you can use against a mobile pawn avalanche of your opponent. Firstly, you can block it once you find the most suitable squares to create a barrier. Secondly, you can compromise it, E.g. by creating a doubled-pawn. And thirdly, you can slip with your army behind the chain, finding attractive targets for an attack.
