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| No Repetition (A rule called “Ko”)

No repetition ever

Full disclosure - this is a rule that may confuse you at first. Fortunately, it is not as complicated as it may first appear. I for one (although many would disagree) think that a good ko fight is one of the most fun things you can have in a Go game.

Go games can be really long. However, they must never be endless. To prevent the possibility of an endless game we have a rule called “Ko”.

Just imagine a situation like this one. Given enough stubbornness, those players would be playing until they pass out. (feel free to watch for a while)

ko diagram

To prevent health problems connected with exhaustion, we have this rule:

A completely identical board position must not appear twice in one game.
Therefore, before you can recapture a stone that just captured yours, you have to play elsewhere at least once.

Can you ever capture that stone then? What are your options? Basically, you have two:

⬤ You deem the stone not important for now and play elsewhere, letting your opponent end the ko by connecting her endangered stone if he or she wants to.

⬤ You deem the stone important enough to fight the ko. You still have to play elsewhere (of course) but you try to find a move your opponent will feel compelled to respond to immediately instead of resolving the original ko (we call that a ko-threat). After that, you retake the ko stone and the fight is on!

Confusing? Then check out the following examples. It will be clear in no time.

Black to play

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And on 19x19 board, there are usually much more than only one threat, so the ko fight can span over several moves. The hard part - of course - is judging if any given threat is big enough to respond to or whether it is more beneficial to end the ko. But hey, I said the rules are easy, not the game itself.

Let me get back to this one later
I understand,
what's next?