Positional and Endgame Concepts
Prophylaxis
Definition
Prophylaxis is a strategic technique where you anticipate the opponent plan and prevent it before they can execute. Unlike attacking play that creates your own threats, prophylaxis prioritizes the question "what is the opponent plan?" and moves to defuse that plan.
Usage and Example
Example: you see opponent preparing to play b5 to activate the queen-side. You play a4 first to prevent b5. This is prophylaxis. GM Karpov and Petrosian were prophylaxis masters in their era.
Grandmaster Tier Context
T4 National through T5 Master. Advanced concept that appears after 1800 plus players start tiring of attacking play. Yusupov "Boost Your Chess" covers prophylaxis.