Prophylaxis (chess) facts for kids

Prophylaxis is a special word in chess. It means taking action to predict and stop your opponent's plans. These moves are often called prophylactic moves.

A famous chess player named Aaron Nimzovich introduced this idea in his book My System in the 1920s. He taught players to think ahead and prevent their opponent from doing what they want.

Thinking Ahead: Simple Examples

Pirc Defence: 1.e4 d6

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

White's next move 9.h3 denies the square g4 to the black B & N, and prepares the developing move 10.Be3

One simple example of a prophylactic move is when a player moves a pawn forward, like h3 or h6. This move can do a few things. It can stop a back rank mate, which is when your king is trapped on the back row. It can also prevent an enemy bishop or knight from moving to a strong square like g4 or g5.

In the diagram above, the world champion Karpov played h3. He wasn't worried about a back rank mate. Instead, he played h3 to stop Black's bishop or knight from going to g4. This move also helped him prepare to develop his own bishop to e3.

Advanced Prophylaxis: Nimzovich's Game

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Black to play

Some prophylactic moves are very tricky. Even experienced club players might not think of them. In this example, Nimzovich himself was playing as Black. He wanted to push his king's pawn (KP) forward to make it a passed pawn. A passed pawn is one with no enemy pawns in front of it.

However, just pushing the pawn directly (1.... e5) would not work well. This is because White could then push Black's king back with checks. For example:

1.... e5

2.fxe5 fxe5

3.g4+ hxg4

4.hxg4+ Ke6

5.Rd6+ and the black king is stuck.

Nimzovich found a clever way to avoid this problem. He played:

1.... Rf8!

This move prepares for future pawn pushes. Now, if White plays:

2.Be1, Black can play g5!

Then, if White takes the pawn:

3.fxg5 fxg5

4.g4+ hxg4

5.hxg4+ Ke5+

This move creates a discovered check and wins White's rook!

To stop this, White needed to play a prophylactic move too. White should have played:

2.Kg1.

This move would have prevented the discovered check on the f-file. Nimzovich's opponent did not see this. Because of this, Nimzovich went on to win the game. This shows how important it is to be aware of prophylactic moves in chess.

See also

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