001. Pawn endgames - The square rule

The square rule

The question in the diagram below is whether the black king can stop the white pawn.
There are three options here:
1. You calculate everything move by move, i.e. 1. h4 Kd6 2. h5 Ke6, etc. However, this is very laborious and you can easily make mistakes.

2. You simply count the moves that the white pawn needs to get to the 8th row. You act as if Black never moves. In our example we get 5 moves. Then you count the moves that the black king needs to get to h8. That's also 5 moves, so the black king will capture the white pawn. This system is not bad and is often used in pawn endgames.

3. But there is a third, elegant option here. The square rule:

The king is able to stop the pawn if he is in the pawn's square. The pawn square is the square you get when you draw a diagonal from the pawn to the 8th rank.