How to form a framework barrier indirectly

It is White's turn to play. The marked white stones are in imminent danger. In this position White does not have to agonise over whether to try for a framework barrier or not. In order to gain sufficient eye space for life, it is the only plausible option! But here a direct approach would seem not to work. Independently both the A-B and the B-C framework links are secure.

However, by applying certain principles ....

Indirect attack

Black 1 is dropped into the largest gap, not in anticipation of breaking the A-B link, but just to create a weakness. Black has a number of ways of answering - black 2 which straightforwardly attempts to re-establish the link is the most instructive. Now White immediately switches the attack to the other link. Again, white 3 is played just to create a weakness. To maintain the B-C link black 4 is just about forced.

But now white 5 peeps at two gaps. If Black blocks at
D then White will play at E and vice versa. In the next two diagrams we shall explore what can happen next assuming that Black resists to the maximum extent ...

Black 6 blocks at E

White 7 pushes towards the edge. After the black 8, white 9 forced exchange, Black has to come back to block with black 10. After two forcing moves White again switches the attack to the other link. If Black is to maintain the link, then black 16 is forced. White 17 is played to steal a black eye. Black 18 and 20 are both forced. White 21 is played at white 15 to force black 22 at white 17. White 23 forces black 24 at white 15 producing a solid mass of twelve black stones.

White 25 secures the life of the white corner stones. After which the isolated black group has insufficient eye space and, compared with the surrounding white stones, too few liberties to live.

Black 6 blocks at D

White 7 pushes towards the edge. Black 8 (atari) blocks. White 9 extends threatening to capture a single black stone. Black defends the stone with the black 10 atari exchange and then defends black 8 with the descent towards the edge, black 12. White 13 gains a liberty. Black 14 is forced. White 15 (cut) and 17 force black 16 and 18. With white 19 the attack switches to the corner framework stone. Black 20 and 22 are forced. White 23 connects forcing black 24 to disconnect the white stones. The white 25, black 26 forced exchange mends a defect in White's stones. The white 27, black 28 exchange strengthens the isolated white stones. Finally White attacks the A group. For these black stones there is no escape!

Black tries a symmetrical defence

The diagonal black 2 attempts to strengthen both framework links at once. However it leaves the A group weaker than before. White 3 forces black 4. White 5 threatens to connect but black 6 threatens to capture three white stones and connect the black stones to the centre. White 7 calmly defends. Black 8 cuts off White's edge stones and threatens to capture a further single white stone. After the white 9, black 10 exchange, White defends with white 11 aiming at breaking the B-C link. The black 12, white 13 exchange changes little. Black must go back to play black 14 because a white stone at H would otherwise kill these stones. So White gets to attack the B-C link!

The black 16 response to white 15 is an overplay. It stops White from playing there and thus immediately isolating the
C stones. But after white 17 and 19, if Black defends his three stones by playing black 20 at F, white 21 at G will ensure that White can kill the six stones in the C group.