Ko (2)

●	Ko fights
	Let's have a look at a game to see how ko fights actually take place.
	Dia. 1	Dia. 2
	In Dia. 1, one White stone is in atari, so Black captures it with 1 in Dia. 2. According to the ko rule, White can't immediately capture Black 1. He must play one move elsewhere (called a 'ko threat') first.
	Have a look at the right side of the board in Dia. 2. Four White stones are surrounded by Black. Also, five Black stones are surrounded by White.
	If Black plays two moves (the yellow crosses), the four White stones will be captured. If White plays three moves (the blue crosses), the five Black stones will be captured. Since White needs to play three moves and Black only two, Black is ahead by one move, so the White stones are already doomed to be captured. However, White can try playing ko threats here.
	Dia. 3
	White answers Black 1 by playing at 2. Now both the five Black stones and the four White stones can be captured after two moves by the opponent: they now have the same number of liberties. White is saying to Black: 'If you ignore my move, I'll capture your five stones.' Well, what does Black do now? Black 1 is in atari. If he connects (to the right of 1), that will finish off the ko, but then disaster will strike his five stones on the right side.
	Dia. 4
	If Black connects at 3, he finishes off the ko here, but White gets to play an extra move on the right side. When he plays at 4, he captures the five Black stones, and the four White stones below come back to life. White gets a large territory on the right.
	Dia. 5
	Black defends on the right side by playing at 3 (Dia. 5). White has played one move elsewhere (his ko threat at 2), so he can now recapture the ko with 4. Since it is a ko, Black can't immediately retake the White stone. He has to play one move elsewhere first.

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