Dochi Yose Tesuji
In a game played on November 24, 1705 between Honinbo Dochi (Black) and Yasui Senkaku (White), Dochi seemed to be losing by a few points in the endgame, when he suddenly played a brilliant endgame tesuji.
The invasion does not work if it is played after the hane-connect sequence.
You may wonder whether White has no other way to play:
The other reasonable move for White is to play 4 here instead of a. Black next plays 5 and 7. If this is not sente, White has refuted Black's play.
is an eye-stealing tesuji, as it makes the eye at a false, but is a good response and Black's attack runs into nothing. No matter how hard he tries, e.g. with and so on, Black cannot get a seki, ko, or anything else.
The solution for Black is to play on White's vital point himself, with .
As can be seen, if White did not reply, he would lose his corner territory (in a seki with Black). Therefore, White had to add another move to defend his territory after Black played hane-connect at the top border. The hane became Black's sente and enables him to win the game.
If Black continues playing inside, e.g. with 233 at here, there is no real difference to the game. At worst, Black has lost a ko threat.
Anonymous : is self-atari. Thus is called into question.
Anonymous2: The author should indeed reconsider