What is 'control?'

Question

One of the important factors to take into account is 'control' of squares, ranks, files and diagonals. But what exactly, does it mean when we say that a player 'controls' space?

The reason I ask is that many, many times, I have seen commentators say 'white plays Re1 to control the open e-file'. I was looking at a game some time ago, and sure enough, this comment was made. But when I looked at the postion, the only other square that the rook could occupy WITHOUT BEING CAPTURED was e2. It couldn't occupy any other square along that file, all of which were covered by black. So, how can you say that the rook was 'controlling' the e-file?

Answer 1

Controlling squares or lines means that the other player cannot contest that square or line without taking a loss, such as in material.

Let us consider an endgame:

[FEN "4k3/8/8/4K3/4P3/8/8/8 w - - 0 1"]
[StartPly "1"]

1. Ke6 {[%draw full,d7,green][%draw full,e7,green][%draw full,f7,green]} Kd8 2. Kf7 {[%draw full,e8,green][%draw full,e7,green][%draw full,e6,green]} Kd7 3. e5 {[%draw full,e8,green][%draw full,e7,green][%draw full,e6,green][%draw full,d6,green]}

After 1. Ke6, the king controls the d7, e7 and f7 squares, as black cannot go to those squares, and so on.

Answer 2

The usage of the word "control" in chess actually does fit its lexical definition pretty well:

to exercise restraining or directing influence

If the rook on e1 in your example restrains the opponent's pieces to occupy squares on that file, he does have this influence.

At the same time, since he can't move very far, these pieces do have "control" of (most of) the e-file at the same time.

"Control" is not binary, and you might have been confused by the assumption that it is. Between full white control and full black control of a square, there are many shades in between. E.g., in your example, both sides have some "control" over the e-file. They can't advance first, but they can punish the other side if it does. There are other cases where the control is more absolute and the controlling side can occupy the controlled squares whenever it wants to.

A piece doesn't even need to be able to occupy a square in its next move to exercise "control" over it! For example, a fianchettoed bishop often has some form of control over its diagonal, even while a friendly knight still sits in his way (because there always is the threat of it moving away). Or, in your example, the rook may still "control" the e-file with a white bishop on e2 (to a lesser degree. It mostly restrains the black queen).

Another form of "control" is by bodyblocking the opponent's pieces from reaching some square(s). This is often meant in sentences like "White's last pawn move allows him to control more space" - the actual number of squares the pawn can control directly is fixed(2), but it now might also restrain the opponent from occupying the squares behind it (depends on the context).