Prophylaxis

In the game of chess, prophylaxis or a prophylactic move is a move that stops the opponent from taking action in a certain area for fear of some type of reprisal. Prophylactic moves are aimed at not just improving one's position, but preventing the opponent from improving their own. Perhaps the most common prophylactic idea is the advance of the rook pawn to avert the possibility of back rank mate.

The above position is from Karpov-Yusupov, Moscow 1983. Muller explains that "The knight maneuver ...Na5-c4 had to be prevented." Therefore, Karpov played 29.Rc5!, an example of prophylaxis.