What does prophylaxis mean in chess?

Preventing the opponent’s plan before it begins. The term was popularised by Nimzowitsch and applies to any move whose main purpose is to stop something rather than to do something.

Is prophylaxis good for beginners?

Yes. Asking what the opponent wants before each move prevents more blunders than any tactic drill, and it needs no theory.

Prophylaxis · quiz of 2

Pro

Prophylaxis

Before every move ask: what does my opponent want to do? Prophylaxis means preventing the opponent’s plan before it exists. The best players spend half their time on it; a single quiet move can neutralise a whole attack.

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About this lesson

Black wants to play ...Nb4, hitting the bishop on d3 and the c2 square. White plays a3. One tempo spent, one idea gone. That is prophylaxis: stopping the opponent’s plan before it exists. It is the least glamorous skill in chess and the one strong players spend most of their clock on.

What you will learn

How to find the opponent’s best move first, and how to use it to choose yours.
The small pawn moves that are usually prophylactic: a3, h3, ...h6, and what each one stops.
Prophylaxis against a whole plan, with Petrosian’s g4 against the King’s Indian ...f5.
Why luft on the back rank is the most important preventive move of all.

The idea, position by position

The lesson is built around four moments. A middlegame where ...Nb4 is coming and a3 takes the square away. A set of small pawn moves, h3 against ...Bg4, ...h6 against Ng5 and Bg5, a3 against ...Nb4 and ...Bb4, each removing an idea rather than making one. A King’s Indian where Black’s entire strategy is ...f5 and White plays g4 to make it impossible, then expands on the queen side at leisure. And a position where a pawn on a7 looks free, with a back rank behind it that should make you pause.

Club players look only at their own ideas. They ask "what can I do" and never "what does my opponent want", and the game becomes two plans running in parallel until one lands first. The remedy is a habit: before every move, name the opponent’s best reply. If it is strong, stop it. If it is not, carry on. The second mistake is grabbing material without checking the back rank.

How to practise it

When you reach the quiz, the first position has an a7 pawn that looks free and asks whether it is; the second asks what Black threatens and how you stop it. Answer with a move, by voice or by tapping. This is a Pro lesson; King Safety and Pawn Breaks show the plans you will most often be preventing.

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Questions people ask

What does prophylaxis mean in chess?: Preventing the opponent’s plan before it begins. The term was popularised by Nimzowitsch and applies to any move whose main purpose is to stop something rather than to do something.
Is prophylaxis good for beginners?: Yes. Asking what the opponent wants before each move prevents more blunders than any tactic drill, and it needs no theory.

Guides

Read the guide, then drill it

A daily chess training routine you can keep 6 min read