Possession of open Lines

Important lines are files, ranks and diagonals. Control over these lines have significant influence over evaluation of a chess position and if other points are equal leads to a  better game. There are four strategic plans based on fighting for different types of open lines.

1. Breakthrough in the centre. This helps in mobilizing your forces fast to any part of the board.

2. Breakthrough between the centre and the flank. This plan works on the c and b files.

3. Attack on the edge of the board. The queen rook file (a file) is the farthest from king in short castled positions. Opening of the outside diverts opponent's forces from his kingside towards queenside and provides an opportunity of opening his king side. This often leads to outside passed pawn to which plays a significant role in pawn endgames.

4. Dangerous diagonals. Entire opening systems (like King's Indian, Sicilian Dragon etc. for Black's dark squared bishop and Reti and English Openings etc. for White's light squared bishop) have been created in which right from the first move, battle is focused on opening and controlling the long diagonals on which the bishops can display their strength. Quite large sacrifices are sometimes made to control the long diagonals. Many times a player gives up his rook in exchange of opponent's bishop to gain control over long diagonal.