One-Two-Three example 1
In this variation (Gokyo Shumyo, Section 1, Problem 95 / Attempts) White must capture the two stones or the two stones to win the fight in the corner. The question is, does White play directly at a, or at b first?
It is probably easier to read the variation where is at b of the previous diagram. Then and will follow. Clearly Black should only play Black c, White d before going back to as a way of giving up the stones. Otherwise the one-two-three principle definitely applies: White gains from having the stone at d.
Then White can play and to capture the stones (discussion of various nets at net example 8).
But White can just bend with anyway. The end result in this diagram is the same as before, except that White previously had given Black a stone with White a, Black b. That's a clear loss.
Also with this way of playing Black has no chance of the Black c, White d exchange mentioned before.
Therefore this serves as a definite example of the 1-2-3 principle in fighting.