where pieces can access most of the board. Center control allows more movement and more possibility for attack and defense. Chess openings try to control the center while developing pieces. Hypermodern openings are those that control the center with pieces from afar (usually the side, such as with a fianchetto); the older Classical (or Modern) openings control it with pawns. Initiative The initiative belongs to the player who can make threats that cannot be ignored, such as checking the opponent's king. They thus put their opponent in the position of having to use their turns responding to threats rather than making their own, hindering the development of their pieces. The player with the initiative is generally attacking and the other player is generally defending. Defending pieces It is important to defend one's pieces even if they are not directly threatened. This helps stop possible future campaigns from the opponent. If a defender must be added at a later time, this may cost a tempo or even be impossible due to a fork or discovered attack. The approach of always defending one's pieces has an antecedent in the theory of Aron Nimzowitsch who referred to it as "overprotection." Similarly, if one spots undefended enemy pieces, one should immediately take advantage of those pieces' weakness. Even a defended piece can be vulnerable. If the defending piece is also defending something else, it is called an overworked piece, and may not be able to fulfill its task. When there is more than one attacking piece, the number of defenders must also be increased, and their values taken into account. In addition to defending pieces, it is also often necessary to defend key squares, open files, and the . These situations can easily occur if the pawn structure is weak. Exchanging pieces To exchange pieces means to capture a hostile piece and then allow a piece of the same value to be captured. As a rule of thumb, exchanging pieces eases the task of the defender who typically has less room to operate in. Exchanging pieces is usually desirable to a player with an existing advantage in material, since it brings the endgame closer and thereby leaves the opponent with less ability to recover ground. In the endgame even a single pawn advantage may be decisive. Exchanging also benefits the player who is being attacked, the player who controls less space, and the player