High invasion of mixed three space extension

Invasion  

is not as common as the invasion at a (see low invasion of mixed three space extension), because Black's response at a will usually connect the two black stones together. Alternatively, Black may choose to attack with b. alone is usually not a good play: usually is used in conjunction with a white stone at c.

Unreasonable: White cuts  

Trying to cut with is unreasonable. In this diagram, White has achieved nothing. If is played at , Black will cut at .

White lives too low  

Trying to live this way is too low for white, and tends to give away too much influence to Black. Later, Black a will capture .

White sacrifices  

Normally the wedge at is too big a sacrifice because it gives Black a ponnuki, but in some specific situations separating may be worth the sacrifice. In some other situations may be played at a, but Black b can seal the white group in.

When White has a supporting keima  

With the stone can be a more severe invasion than . When tries to connect, and works in co-ordination with . Then is placed in an excellent position, at the vital cutting point.

Another idea with a keima  

Charles In examples from actual pro games, the previous diagram occurs; but other variations do, too. For example here before rescuing the cutting stone .

Also, Black may simply play tenuki after the invasion, treating the whole area lightly.