What is the opposition in chess?
Two kings can never stand next to each other. That single rule is where the opposition comes from.
Opposition means the two kings stand on the same file, rank or diagonal with exactly one empty square between them. In this article the kings stand on e5 and e7, with e6 empty between them.
Whoever has to move must step away. The other king can then step forward and take ground.
So the player who does not have to move is the one who gains. Chess players say that player "has the opposition".
Why does the same position win one way and draw the other?
Look at the position above. White has a king on e5 and a pawn on e4. Black has a king on e7 and nothing else.
With Black to move, Black has to step aside. White walks round the black king, reaches f7 or d7, and the pawn walks to the last rank. White wins.
With White to move, White has to step aside instead. Black copies every step and keeps facing the white king. White can never get round, and the game is drawn.
Nothing on the board changed. Only the turn changed.
How does the drawing side finish the job?
The defending king has one job: stay in front of the pawn.
When White finally pushes the pawn to e7 and gives check, the black king steps back onto e8. White now has to guard the pawn with the king, and the only square for that is e6.
That leaves Black with no legal move and no check against the king. This is stalemate, and stalemate is a draw. Many players who were winning have thrown the point away exactly here.
What are key squares?
A key square is a square where your king wins the game whoever is to move. You no longer have to worry about the opposition, because the position is already won.
For a pawn on the second, third or fourth rank, the key squares are the three squares two ranks in front of it. This rule is for pawns on the b-file to the g-file.
- A pawn on e4 has key squares d6, e6 and f6.
- A pawn on e3 has key squares d5, e5 and f5.
Now check the first position again. White's king is on e5 and the pawn is on e4, so the king is not on a key square. That is why the turn decides the result.
The rule to remember: king in front, with a spare pawn move
Here is the same idea in a position White wins whoever is to move.
White has the king on e5 and the pawn on e3. Black has the king on e7. Because e5 is a key square for a pawn on e3, White is winning already.
With White to move the winning move is 1.e4. It is a pawn move, so the white king stays exactly where it is, and the turn passes to Black.
That is the rule worth learning. Put your king in front of your pawn and keep one spare pawn move in hand.
The mistake we see learners make
Learners push the pawn first and bring the king afterwards.
The pawn then arrives in front of the king, and the king cannot get past it. That is the drawn position on this page, and it is a draw no matter how well you play from there.
The habit that fixes it is short. King first, pawn second. Push the pawn only when it gains something, or when you need to pass the turn.