Game 4 Carlsen- Anand Sochi 2014

Game 4 was by any measure, the most technical struggle so far in this match.  It featured play around the theme of an Isolated Queen's Pawn (the "IQP" or Isolani), one of several types of common central pawn formations.

Carlsen poked and probed away with white. But Anand was never worse (he may even have been better at some stage) and defended quite comfortably. The draw was a just and predictable conclusion by the time the perpetual check happened.

One unusual aspect of this match is that we have seen different central pawn formations in each game.  Game one saw white adopting a big central pawn roller. Game two was played around a fixed symmetrical e4/e5 formation. Game three started symmetrically (d4/d5) but it then turned into dynamic formations.

The central pawn formation is like the physical terrain in a battle. Like physical terrain, pawn structure cannot be changed easily. Plans and tactics must be appropriate to the structure. Every theorist (and of course, every decent player) has devoted some time to understanding typical plans and themes arising from different central pawn structures.

Before going into technical details about IQPs, allow me to move mildly off-topic. In May 334 BCE, the Persian army was deployed on the East Bank of the River Granicus (now the Biga River in modern Turkey). The Greeks, led by a 21-year-old with very little battle experience, arrived on the West Bank.

The battle that followed turned on one action. Alexander the Great swam his horse across the river and planted his personal flag in the middle of the Persian lines. His forces including the famous Companions followed in order to protect him. Alexander took several wounds but his army won the ensuing melee.

An IQP is a bit like that flag planted in the centre of a chessboard. The Isolani is exposed and difficult to protect. But it stakes a strong claim to space and it can be a rallying point.  IQPs can arise from multiple systems, with either colour including set ups as different as the Sicilian Defence, the Caro Kann, the Nimzo Indian, the Queen's Gambit Declined or Accepted, the Scotch Opening, etc.

Most strategists seem to like playing against IQPs. Karpov often dismantled IQP structures and  Smyslov and Petrosian also made a living killing IQPs. Tacticians like Kasparov and Spassky often played with the IQP. Botvinnik and Korchnoi were comfortable on both sides. Bobby Fischer was also comfortable on both sides.

Fischer forced Petrosian to take an IQP in game 7 of their Candidates match and won a classic. http://www.chessgames.com/perl/chessgame?gid=1044351
Fischer himself accepted the IQP against Boris Spassky in Game 21 of the 1972 World Championship Match and won a convincing game. http://www.chessgames.com/perl/chessgame?gid=1008424

Both games were Sicilian Paulsen Variations. Anand also invited a Sicilian Paulsen in game 4 but Carlsen declined to get into the open mainlines.

Now take a look at the diagram.

It's the Carlsen -Anand Game 4 pawn structure stripped of pieces. Similar things can arise with colours reversed.

The player with the IQP (black over here) controls two strong-points, c4, e4, due to that pawn. He can put Kts or Bishops on those outposts. He has chances of occupying two open central files, with either Re8 or Rc8. He must play flexibly and actively to make the most of those chances. He should avoid getting tied down to static defence of d5  If he can win control of d4, he would control the entire centre, c4,d4, e4.

Playing against the IQP, there are two high priorities.  White must control d4. If at all possible, he must occupy d4 (the square directly in front of the pawn). Losing control of that square is often disastrous. Control and occupation of d4 means a blockade of the IQP, which then becomes a static target. The second high-priority is to maintain pressure on d5.

Aron Nimzowitch devoted a chapter to IQPs in his classic "My System". His recipe for playing against the IQP was "First restrain, then blockade and finally destroy". A good heuristic, assuming it can be carried out.  

At world championship level, where both players understand the nuances of IQP play very well, neither side is likely to make elementary errors. Carlsen  tried a more complex plan where he changed the pawn structure with a capture on c6 and then tried to break it up with c4. Black accepted an inferior structure and just ensured his pieces stayed active.It was never trivial. It was the kind of position where both sides have to endlessly assess little variations and tricks. It was also objectively drawn.
Some interesting moments from the game.

Diagram after 19. c4 

White intends to capture on d5 and to hit the pawn after cd5 cd5. He also hopes to make something out of his queenside majority, which could yield a distant passed pawn.  But he's put his queen in a strange place and he's cramped himself. 

Several commentators (such as Rajabov & Giri) felt Anand was slightly better here. The engines also say it could be mildly better for black after 19. --Qb7 20.cd5 cd5 21. Bd4 Ne4 Even 19. -- Rc8 or 19. --Bb4 could keep some pressure for black.  Anand's plan of Be4, Nh7 looks odd. Be4 is a normal looking move but it removes the option of Ne4. 
 

Diagram after 24. Nh4 Be5! 

Black has surprised by recapturing Bxd5 and keeping two isolanis on c6, a6. Why?  Probably to prevent a queenside runner and also to chop rooks on the e-file. "Everybody" was expecting cxd5 and that is probably a better move objectively.

After Nh4, Be5! challenges the d4 bishop in timely fashion. A setup with Nf5, Bd4 would be horrible. Now, a lot of pieces will come off.

 Diagram after 27. -- Ne6

White is permanently a little better due to the pawn structure. But black has active heavy pieces and he can avoid being pushed into static defence. All heavy piece endgames are likely drawn. White can hit the pawns but black will find counterplay.  Anand cut the Gordian Knot by pushing the pawn to d4 when it starts looking dangerous and compensates for material deficit.  

 Diagram after 43. h4
Now if 43.-- d3 White has the diabolical mating threat of 44. g5 Qe2 45. Kg2 d2 46. g6 but remarkably 46.--Qe8! 47. Qd3 d1=Q 48. Qxd1 Qxg6+ may still be a draw. But Anand played 43.--Qxa2 when 44. g5? Qxb3+ may give black winning chances.  And so from here, taking the draw by perpetual is a natural end.