4-4 point 3-3 invasion double hane
Initial position
This variation stems from the 4-4 point 3-3 invasion page. Instead of extending at a as in the usual sequence, Black can play the double hane at . Black will do this if he is prepared to take the corner at some extra cost or, if White resists, fences in White in the corner, or to keep the initiative.
Variation 1: taking the corner
A straightforward variation is when cuts and captures what has become a cutting stone. Black can then sacrifice the cutting stone and capture the corner. The double hane has played the role of cut the side you don't want.
- Black has the corner territory
- Black has influence at the top
- White has influence at the left
- White has the initiative
- White has some aji against the corner
If WHite gets the marked stone in place, will either link up as in the diagram or capture the marked black stones.
The other aji is that and
threaten to extract the marked stones in the same way as above, so that
becomes almost absolute sente. This in itself is not so bad, but it could be a minus if Black's reason for not following the standard sequence was that the top side is not interesting.
Variation 2: influence and/or initiative
@
. White must not play
at
or Black will take the corner as in the above, while increasing his influence. In this variation, Black can now take the initiative to play elsewhere, extend his wall around a or increase his influence towards centre and sides at b
Variation 3: White's counter hane
If Black plays the double hane, Black has to be prepared for this . White intends to give up the corner in exchange for a position on the top. In an emergency, however, instead of
Black may play at a; the likely outcome is that he gives up a bit more territory in the corner in order to maintain his outside wall.
After in the previous diagram,
is the joseki move, reaffirming the unity of the black stones. After
, White can secure a base with a move like a or play tenuki.
The presence of extra stones
After the variation "taking the corner" White will most likely continue with these moves. In most cases, when White invades at the 3-3 point, Black has stones on both sides, at or around the places shown here. Black's left side stone has lost much of its value after this sequence.
Black would probably like to play the double hane of in this diagram, but here the aforementioned aji of the marked white stones come into play. White can retake the corner - or worse.
In White's counter hane variation, this atari play is recognised as joseki, but is highly sensitive to stones on the upper side, for example at a or b in thhe following diagram.
These plays occur in pro games. When Black plays , White will eventually have to live at e. Before that White has a chance of pulling out the marked stone with White c, Black d and White continuing on the third line for a while. The books teach that this is good for White if Black has a stone at b, but poor if Black has a stone at a.
If White lives immediately at e and Black tidies up by capturing at c, Black will be thick anyway (possibly slightly overconcentrated).
There's an early example in Chapter 1 of Beauty and the Beast.