Important Pawn Structures
Restrain, blockade, destroy! -- Nimzowitsch
In my 4th and last blog in the series "Positional Elements in Action", the topic regards the exploitation of our opponents weakness. Since this is too broad a subject to be comprehensively covered in one blog, I've concentrated my efforts on the vulnerability of the enemy pawn. This includes a copious list of common pawn structures.
- Isolated pawn
- Hanging pawns
- Doubled pawns (tripled pawns)
- Backward pawn.
I'll elucidate the typical plans and ideas for undermining these various pawn structures. However, in a huge variety of openings one side voluntarily allows their pawn structure to be compromised in the pursuit of other objectives, which include: The bishop pair, rapid development, an open file, a quick kingside attack, or simply the pawn is only weak in "theory" and not cannot be exploited immediately. While the first two structures are common straight from the opening, the last two are usually deleterious liabilities in the position. (With the sole exception for the backward pawn being the Sveshnikov Sicillian 
) I've formatted this informative thesis on weak pawns to include two sample games per structure, a summary of the ideas and common openings arising, and lastly relevant resources for further research of the reader. Without further ado, let's dive right in!
Isolated Pawn 
The isolated pawn is a concomitant the Queens Gambit Accepted, Nimzo Indian Defense, Tarrasch (French Defense), Tarrasch (QGD), and others. The side playing with the isolated pawn is sometimes trying to initiate a kingside attack (QGA, Nimzo) or playing on general piece activity not connected with an attack (Tarrasch French and Tarrasch QGD). Frequently black's plans against the isolated pawn with include blockading the pawn while trying to stymie potential kingside expansion by white. White's ideas usually aren't as connected with blockading an isolated pawn. White's more involved with attacking and capturing the pawn. Naturally, this disparity in course of action between white and black fighting the isolated pawn is that black's primary goal is equalizing and white's primary goal is seizing the advantage. Although, this isn't necessarily always the case as we'll find out in the following game which is the epitome for when one should swap the isolated pawn weakness for another weakness. This is also known as the transformation of advantages. Karpov was the greatest player of all time in playing against the isolated pawn.
Hanging Pawns
The hanging pawns structure is a frequent guest in the Nimzo Indian and Queens Indian Defense (the NID and QID, respectively). Like the isolated pawn, hanging pawns can be an asset or a liability. The side playing with the hanging pawns usually cannot create a kingside attack (although in theory it's preferable) because of a fienchettoed kingside bishop defending the king. Instead, they are typically playing for overall control in the position and are playing for active pieces. If white has a pawn on b3, black frequently played a5-a4 to seize activity. Although the pawns control a lot of squares, if one of the pawns is provoked to advance, this could end with catastrophic weaknesses. For instance, take the following games.
Doubled Pawns
Doubled pawns are commonplace in the Winawer French, Trompowsky Attack, Petroff Defense, Sicillian defense, Nimzo Indian and everywhere in between. They're typically ubiquitous liabilities in positions where the opponent has just ceded the bishop pair and the compensation is the doubled pawn weakness. In most cases the side with the doubled pawn in either plain worse (due to the weakness) or has the bishop pair, or an open file to compensate. I do not wish to dwell on the theoretical standpoint of openings with doubled pawns. Rather, I would like to provide two examples which elucidate the consummate exploitation of the doubled pawns in the middlegame. Albeit one of them being a cutthroat knockout!
Backward Pawn
By itself, a backward pawn is an almost certain curse, as it leaves a gaping hole in front of it and it's usually irreversible. (Either it lingers the whole game or gets captured) A rare exception is the rich Sveshnikov Sicillian where in nearly every case black is getting some good compensation (bishop pair, white's weak dark squares, active pieces) and it's also sort of a "pseudo backward pawn" as it can push d6-d5 fairly easily. A true backward pawn would have both pawns on c4 and e4 making d5 virtually impossible to execute. The following games are both Sveshnikov's (any other backward pawn positions are usually too favorable for the side playing against the backward pawn, and less instructive) where white limits black's counterplay while exploiting the weaknesses. It's especially interesting to see how effortlessly GM Gata Kamsky fell apart with hardly anything special on white's part.
For further investigation...
I highly recommend Andy Soltis's highly acclaimed book, Pawn Structure Chess. The book is a comprehensive work on all pawn structures, not just the ones mentioned in this blog. My favorite chapter is Stonewalls and Other Prisons. I like his writing style and examples.
Reading any Chapter of Watson's monumental works on Chess Strategy (Chess Strategy in Action and Secrets of Modern Chess Strategy) will be more productive than reading multiple other books on strategy. It's not just about pawn structure, it's about the development of positional theory. Piece play, piece imbalances, the bishop pair, everything! Watson's systematic approach of formatting the book and eloquent writing style make it an irresistible read.
I am compelled to recommend Watson like works such as the antiquated My System by Nimzowitsch which is the foundation of modern Positional understanding. It's historically the first documented working exercising positional "theory". Another book is Dynamic Chess Strategy by Mihai Suba, who expresses his ideas in a humorous writing style. It's largely comprised of his own games so it's also a good games collection book. Although, there are also other famous players' games included as well.
As for puzzle books, I recommend especially for advanced players (elo 2000+) Jacob Aagaard's Positional Play. The book is formulated around three essential questions: What are the Weaknesses? What is the Worst placed Piece? What is my Opponents Idea? Hence chapters such as Weaknesses, Piece Play, and Prophylaxis address the topic of those questions. Many puzzles are sprinkled throughout the book, and Aagaard has an intriguing philosophy of how to think about positional chess.
