The way modern chess is played is based on principles founded by Steinitz. You can read his work in his book The Modern Chess Instructor (< that is a vague recollection of the title).

I had a thought regarding his idea about equilibrium and attack and defence, and thought of putting principles and explanations to the concept. V

Principles of the offense and defense in order of priority:

Offense (with the initiative)

1) Safety - The protection from danger (The condition of being safe; freedom from danger, risk, or injury.)

This principle is justified as the goal of chess is to capture the enemy King (checkmate) and that if a unit is threatened it may be considered unsafe and can be captured and removed from the chessboard on the next move.

2) Activism - The creation of threats (The use of direct, often confrontational action, such as a demonstration or strike, in opposition to or support of a cause).

This principle is justified on the premise that chess is a turn based game and that due to the priniciple of safety a threat must be addressed next move limiting the opponent's choice and number of moves. This rule is tied to the initiative.

3) Dynamism - The creation of progress (Continuous change, activity, or progress; vigor.)

This principle is justified by the positional concepts of space, mobility and centralization. By deploying a unit dynamically you take up space, limit the mobility of the opponent and hence limit the choice of reply.

Defense (without the initiative)

1) Safety - The protection from danger (The condition of being safe; freedom from danger, risk, or injury.)

2) Retaliation - The creation of a counter offense (make an attack or assault in return for a similar attack)

This is the defensive counterpart to Activism whereby this saying comes from "The best form of defense is attack".

2) Economy - The management of defenders (Careful, thrifty management of resources.)

In a defensive position. Management of defenders is vital for freeing up the function of more important units, thus giving more of an opportunity to use these pieces for the principles of retaliation.