Herman: might not be the first move you consider. It is surprisingly effective, however:
This is answered by . Black cannot prevent the marked white stones from connecting out due to a shortage of liberties.
Connecting at prevents the shortage of liberties. But after -, black is again caught by a shortage of liberties.
The other way to prevent the connection under is to play immediately. Now, is the tesuji white is looking for. After , black cannot play a due to shortage of liberties. and are miai, if black plays at , white connects with at , and black still ends up with a false eye.