What is a ko-threat?

In a “dictionary” sense, what exactly is a “ko-threat”?

How to use it in a sentence?

From what I learn here:

No Repetition (A rule called “Ko”)


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!

So, to expand the sentence, may I say that all statements bellow are true?

  • A ko-threat is a move
  • A ko-threat is an important move
  • A ko-threat is an important move you play that threatens something elsewhere that you hope your opponent needs to respond
  • A ko-threat is a move that threatens something somewhere else that you play with the intention of making your opponent unable to fix the ko, so you can have the turn again and win the ko

Thus: “he played a ko-threat” means that “he” made an important move elsewhere with the intention of deviating the opponent move and having back the turn to play in the ko.

Am I using the term grammatically right?

Puzzle 3:

Yes, the start is the same. This time however, White has something to threaten because there are other, not yet completely settled, stones on the board. White’s move (at D2) is what we call a ko-threat.

This puzzle is great.

Black can choose to ignore the threat and finish the ko but that means he will lose all his bottom stones now. The hard part of ko fights is judging who has more threats and how valuable they are.

So, next time I hear “this is a ko-threat”, I can finally understand that there is a ko fight somewhere else and the ko-threat is a move made to distract the other player from the fight, getting back the turn to play on the ko itself, wining the fight.

I hope I made sense of it, and if so, other beginners can also understand. But if it is wrong, please correct me there.

Thanks! :sweat_smile:


Great stuff!

I’m not a native speaker, but to all I know: YES!


To make it extra tricky, you can play ko-threats even when there is no ko!

It’s usually bad, since you should save threats for the occasion that you actually need them to defend an important ko. Additionally it usually removes potential weak points in your opponent’s defence. These potential weak points, create “opportunity”, also called aji (which means taste), and removing them is called aji-keshi (taste removal).

However, it is often a great strategy to play a ko-treat just to get some more time to think if your clock starts to run low. Jokingly called a timesuji, which is a pun on tesuji (a clever and appropriate move, often surprising to those that don’t know it)


Mh… but then they’re just threats, not “Ko threats”, no? :wink:


You do have a point there…




@drbeco I think you are totally right. The only thing I would maybe clarify is that a ko threat doesn’t “distract” the opponent from the ko fight, it is part of the fight. You can often calculated the exact number of points at stake if a ko is won or lost and also calculate the number of points a given ko threat is worth. If the threat is worth more then it should be answered and the fight continues. If the threat is worth less then it should be ignored and the fight ended (by filling in the ko). So I would say it’s not a distraction but rather a fundamental aspect of how a ko fight is played out.

If you are much stronger than me you can work out the number and value of all the ko threats on the board for yourself and for your opponent and hence determine who should win a ko fight before you even set one up…


Just to add to the other replies:

you can imagine when playing a ko threat, that you’re asking your opponent “can I have two moves in a row on this part of the board?”

If they say “no” by answering your move, you can retake the ko and fight on.

There is then value in both winning and losing a ko. Winning the ko usually gives some local gain or gain nearby on the board - maybe you kill/save some stones or cut some stones off or connect two of your groups etc.

However you probably had to ignore your opponents last move to end the ko, so they’ll get two moves in a row elsewhere.

There’s a good bit of variety to the types of ko that can come up on the board. But that’s another discussion I guess :slight_smile:


This can be formalized with the concept of ko master. However, precisely working out these calculations requires one to dive down the rabbit hole of combinatorial game theory (which I thoroughly fail to grasp).


Nice rule I’ve read in the komaster link.

Some ko fights , including many ordinary direct kos, don’t require ko threats , because the alternative to winning the ko is just as good – this is often true, since kos become interesting when they have roughly the same miai value as the biggest plays elsewhere. If losing the ko is as good as winning it, then why waste ko threats you might need later?

Ko is so important in the game of go, that I start to think it is the very soul of go. Go should be renamed Ko (or Baduko, or Weiko).

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Ko is an important concept, but I don’t think it is the central one. In fact, it’s possible to reasonably play an entire game without ever even creating a ko situation.

I would consider life and death to be the central concept around which Go strategy revolves.


Most games I play do not have a group dying or struggling to make eyes for either player, so by the “reasonable to play an entire game without creating ko”, life and death isn’t central to go either.

The only thing that I can think of that no game avoids, are shapes.


Sure, games could be played entirely without any stones dying or even struggling, but I still think the way that moves could potentially threaten stones are what drives how efficiently one can safely surround territory. I don’t think you can say that any of your games do not have any moves that are ultimately affected by life and death concerns. Even though a group may never be in any real danger of dying, an attack on a weak group can force one to make additional moves to ensure its safety, which may come at the expense of missing more profitable moves elsewhere.

I think the crux of go strategy is figuring out how to balance the concerns of safety and ambition while building up territory, and the concerns about safety are ultimately life and death considerations. If one plays very cautiously to absolutely prevent their stones from dying, how could one say that concern about life and death is not a major driving factor in their play?

Even at the end of any game, the meaningfulness of territory can only derive from the stable life of the stones surrounding it, and the futility and unavoidable death of any enemy stones that might try to invade.

You mention shape as being ubiquitous, which of course I agree with, but what is “shape” if it is not concerns about how to both safely and efficiently control territory?


I have seen games being played without either player making shape!

I declare that the most essential part of Go is Placing Stones!

(or is it…?)


Have you never seen a game where both players just immediately pass and walk away in peace?

The only winning move is not to play.


If I may, this is exactly what Go seems to me to be about. No wonder it was conceived in an empire. Especially an empire known for valuing tribute over spoils of war.


Actively making shapes, and “making a shape” are different things.

I’d like to see a real, ranked game played out that does not have a single iron pillar or a one space jump in it.


And what key moves do you play that “concern the safety of a group”? Shape moves…

What moves do you play that don’t concern the safety of a group, but help increase territory or potential? Shape moves…

What moves do you see played by beginners that feel “wrong”? Moves that aren’t shape moves…


I’m not questioning the importance of the concept of shape.

Rather, my arguments are meant to counter this statement:

which appears to be an assertion rather than just a rhetorical device, since you follow it with:

I disagree with your statement that “life and death isn’t central to go”, since I think life and death are fundamental for understanding proper shape and even more basic concepts like territory.

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“Ko is an important concept, but I don’t think it is the central one. In fact, it’s possible to reasonably play an entire game without ever even creating a ko situation.”

You can replace “ko” with any other concept in Go and it isn’t any more valid. I’m just pointing out that your original assertion doesn’t hold up. Trying to say that Go only relies on one concept, or that “one idea is more fundamental than another” doesn’t make sense in this game. You can also technically play Go without caring about the life/death status of a group and still win.

Not judging what moves are actual ko-threats in a ko fight is wrong. Not caring about life and death in Go is wrong. Playing shape moves because they’re shape moves is wrong. None of this means anything, and getting into arguments in a thread about a guy trying to organize his thoughts and learn Go isn’t helpful. The guy was really excited to find out about ko and how much it affects games, something that is honestly really crazy especially when you see a pro game and they play an early ko at like move 20 and declare that that they’ve won as they’ll ignore any threat and will fill the ko.