Opposition: which king can go?
I started reading my book. And the first point I need to focus on is called the "opposition".
This is the battle between two kings. Not very useful, in all honesty, but quite interesting. And I need to write this post to be sure that I completely understand the concept.
So here it is. To "have the opposition" means to be in a winning position. I took a while to familiarize with this meaning because in my mind, "to have" the opposition can be meaning that you are suffering the opposition. But maybe it is just a problem of language.
Anyway, once I finally got that "to have" the opposition means to be in a winning position (so I said it again and I made more clear to myself) let's see who has the opposition. In this diagram whoever has to move is in a loosing position:This is because whoever moves will give up a square allowing the opponent's king to move forward.
The rule is that whoever has to move when there is an odd number of squares between the kings does not have the opposition. Therefore, to have the opposition, you need an even squares distance. Is it clear?
Let's say it again: to win the opposition, you need an even number of squares between the two kings. Now it should be clear.
This rules applies even in case of diagonals:
In this case there are six squares (b2,c3,d4,e5,f6,g7) so whoever moves will be in a winning position.
But what happens when the kings are not on the same row, column or diagonal? Even in this case you can calculate your position and understand if you are in a winning or in a loosing position. How?
This is curious and of course it will depend from your full understanding of this rule. To be in a winning position you need to bring your king in a square where you can create a same-colour square or rectangle with the opponent's king. What? Yes, I didn't write it in a very clear way. I hope the draw can help:
When you move your king to b2 you create a big rectangle b2-b8-f8-f2. In this moment you "have" the opposition. It means your king is in a winning position.