B2 Bomber Josekis
Approaching a B2 Bomber
WARNING: DO NOT TRY THIS IN YOUR GAMES!
The sequence after is similar to 4-4 point low approach, one-space low pincer, one-point jump.
( at a, at b.) Please note that this is generally considered a special strategy-- white stops the bomber from taking off at the cost of ending up with bad shape AND giving black lots of solid territory. Then again, black's B2 has already enclosed too much territory to begin with!
( at a, at b, at c, at d, at e.)
Black gets a lot of territory on the left but is somewhat overconcentrated.
Both sides follow the wall height + 1 rule.
You might want to first refer to Three Crows, because the invasion should not succeed even with outside support. It might be useful as a pseudo-ko threat against a DDK in the situation above, though.
The marked white stones are not necessary, but they might be useful. This should only be attempted as a last-resort, as you're stopping a B2 by crashing another one into it.
Well, I assume this is a misclick. Even with support as shown, white shouldn't play like this. Black should obviously play elsewhere.
This is a light way to handle Black's B2 bomber. It is far enough that black's B2 influence has little effect on it, yet close enough that it can stop the B2 like a ladder breaker.
This is a possible alternative to  if white wants to stop the B2 without getting overconcentrated.
If white already has three bombers as shown, playing elsewhere is probably the best option.
A Really Bad Example
Please note that the sequences given above should definitely be played when a B2 bomber is already present, because stopping the bomber is more urgent than any another move. The following is an example of what might happen if the bomber is not stopped in time.
through may seem strange, as they are definitely too slow. But they do serve a purpose-- sente is given up temporarily to make a B2 bomber.
Theoretically, black is supposed to make a three-space extension from the wall to a at move 17. However, this is a mistake, because white can now bring the power of the B2 Bomber into action...
Application: Taisha B2 Bomber
Anonymous: 7 is a famous trick play in this line, 8 is a common mistake, White wastes no time in playing at 9. This is a great way to avoid the taisha.
Another Application: Using a probe to get a B2
George Caplan: There is an even more common opportunity to use the decisive properties of the B2 Bomber in actual games. Forgive my first attempt at diagramming, but here goes.
Takemiya Masaki presents this technique in Enclosure Josekis. He specifically cautions against 9 at "a" because the postion will become "overconcentrated" and because of the peeps available to White.
Obviously, this old book is outdated - the time of "shape" and "light" is over - today we play for power and results.
In fact, here is a trick play, trying to induce the peeps that Takemiya warns against. The result? White actually forces Black to make a powerful B2 Bomber formation, at the cost of only one stone!
White's shape here is horrible - the four stones that capture black's first move are ok, but the 3-3 pt stone seems redundant and the rest of White's plays are too close to Black's thickness or hopelessly scattered.
Black, on the other hand, again, with one brilliant sacrifice - forms a perfect B2 Bomber - all in what was originally White's position!
Now, we always should be careful evaluating results without seeing the rest of the board, but it is hard to deny the power of Black's position here. Absent White having a B2 Bomber of his own, in the near vicinity, this has to be a success for Black.
It is indeed fortunate for Takemiya's well deserved reputation that "Enclosure Josekis" is out of print and hard to find.
unkx80: The mistake here is actually to allow trumpet connection at . Since White a or b will only get captured, there is no way to prevent Black from playing both a and b to form the all powerful B2 Bomber.
Alex: Right. White has no choice but to play this way. Black gets to capture one stone with , but after , there is no way for him to make a bomber.
Fighting B2B Joseki
erislover: There is a little-known B2B joseki based off the 4-4 point. Both sides get a bomber and the outcome is wildly unpredictable.
Black starts out with the attach-block sequence. Traditional views of this sequence consider it to be a primarily defensive measure. But recent innovations in thickness and influence have yielded the following joseki:
begs black to make the trumpet connection, anticipating black's desire for the B2B. After the atari kikashi at , white whips out a trumpet shape of her own! This sets the joseki on a forced course up to where both sides get a B2B. The results from this joseki are unclear, but usually considered just slightly better for white due to black ending in gote. This may soon be a rejected bit of conventional wisdom because normal understanding of sente/gote relationships are very unclear around B2Bs.
A typical followup to the Fighting B2B joseki is , threatening to unleash another bomber. Black wisely plays to prevent it from forming.
Another Game Position
Blake: White has no chance to protect her alabaster city in this position; it's best for her to resign.
Celebrir:But White has three hidden B2 Bombers ! (circled Stones) Besides, if it's Whites turn, white gets four more B2 bombers. That makes a total of seven against three B2 Bombers. Now B has to resign !
Anonymous I just want to point out that there are a couple other B2 Bombers White can make