The first time I went to a chess club was a rather deceptive experience. There were few people playing chess, most were playing cards. Two people were playing chess (part of the club championship, as they told me), a women against a man. I remember two things about this game: the woman was almost blind, but was clearly winning, and her opponent was a man and obviously not feeling well in his own skin.
Later two other players began to play chess - I had the impression they did it for me, somehow to show that this was indeed a chess club where people indeed played chess. After the game one of the guys took some time to explain me some moves of the game. In a given position he said that a certain pawn was "weak". I asked him what he exactly means with this, and he could not tell me.
Yes, some terms in chess are very common, but it is not always easy to explain them, at least not at the first go. Today I know that there is a huge literature on weak pawns, with a lot of controversy about how (for example) the merits of an isolated pawn can outweigh its typical weakness. But here I want to take a closer look at the term "control a square" - the motivation for this post was the question of a guy training in Chessable, who wrote:
This is going to sound like a really stupid question, but, here goes nothing! What does it mean when an annotator says that a piece or pawn [or king] 'controls' a square? I mean, what exactly constitutes 'control' over a square? I ask because, as a stuggling ELO1250 player, trying to improve my game, this question comes up whenever you are trying to assess a position.
As Hans Berliner explains, there are different varieties of square control. For those chess players who doesn't know, Berliner was a successful correspondence chess player. His lifetime score was 94 wins, 1 loss, and 10 draws. After he won the 5th World Championship he turned his efforts towards computer programming (backgammon and chess). In his book The System he explains a system he used to guide a chess player to the right moves. In this system he focused on Queen's Gambit from White's perspective. Berliner's system is widely considered as controversial, but it is wonderful work if you are interested in theoretical discussions on questions like "the best opening" or "how to find the best moves".
In the first chapter of his book Berliner gives following position:
As well known, to "control a square" means that a unit could legally capture an opponent piece if it were on that square. Both pawns and pieces are used to control the board. However, pieces are secondary to pawns, as pawns are the least valuable unit in the game.
Berliner differentiates between three varieties of square control: absolute, general and disputed control. In the above diagram White exercises absolute control over d5 and f5, as only White has control over these squares; Black exercises absolute control over d4 and f4.
White exercises general control over g5, c4 and many other squares - neither player has a pawn controlling these square, but White can put a minor piece there safely, and Black cannot. Black exercises general control over no squares.
Disputed control means that neither player can put a minor piece on square safely. In the above diagram, if White were to play c3, he would have a disputed control over d4. However, as Berliner explains, "if a pawn is safely occupying a square, it is not terribly important if the opponent has absolute control, as long as the pawn can safely remain there" (Berliner, The System, p. 20). He went on explaining that this is a very important distinction, upon which much of the opening theory in The System is based:
If the pawns at d4 and d6 were removed from the board, and the c2- pawn were to advance to c4 (see diagram below), the absolute control of d4 by Black would be a serious matter, as White could not put a pawn or piece there, and Black could eventually occupy it with a piece [...] White should play in such a way as never to give up absolute control over an important square that can no longer be occupied by own pawn. (Berliner, p. 20)
Both players have a strong interest to control as much territory as possible, especially in the centre.
Dr. Berliner died recently (in January 13, 2017). The present contribution is a modest attempt to prevent his name and work falling into oblivion.