Taking sente in a ko
A basic point about ko fights that isn't so often emphasised.
If your opponent is the first to capture in the ko, but you win the ko, that is effectively gaining sente. That is, with a long or short sequence like
- Black takes the ko for the first time
- White finds a threat
etc., etc, ...
- Black makes a threat
- White ignores Black's threat, finishing the ko
- Black follows up the threat
at the end we find White has sente, where Black began with sente.
Of course either of these may be true:
- White urgently needs to play near where Black made the threat
- Black urgently need to play near where White finished the ko.
That is, the threat and the play finishing the ko may both be seen as open-ended plays.