Crosscut--technique or aggression?

Diagram 1: This is a typical crosscut. Black 1 attaches to the marked white stone. White answers with a hane (diagonal move) at 2 and Black crosscuts with 3.

Diagram 2 (1-37): This is the semifinal game for the Oza title played between Cho U (Black), the current Honinbo, and Yamashiro, a 9-dan veteran. White ignores black 11 to put pressure on Black with the sequence 12 through 24. White now has the edge as Black's shape is over-concentrated. Because Black feels a little behind, he overdoes things with 35. Playing at 36 probably would have been better. However, Black's intentions become clear when he crosscuts with 36--he wants to start a fight.
If you have your go board handy, play the game until this point, then visualize some sequences to try to get a reasonable result.

Diagram 3 (38-65): White 38 seems a good move until you see Black's response at 39. This move wrecks White's position as Black can now capture White's stones on either side of the crosscut. White 42 and 44 are about the best White can do, but black 47 takes a large corner. In addition, the marked black stones are no longer overconcentrated. They play a leading role in the attack starting with 51 and ending with 65. Black has everything going for him. He can profit even more if he cuts at A.

Diagram 4: Instead of 38 in the game, White should have played atari with 2 and 4 to sacrifice his marked stone. Now he can play 6 in sente, too, as Black has to answer with 7 and 9. White then can choose between playing at A to ensure his stones will live or attacking Black's stones with B. If Black plays at C, white D weakens the marked black stones.

Diagram 5: White probably hoped Black would play at 3, allowing White to play the tesuji (locally clever move) of 4, which would lead to the sequence through 8. Black has to defend the corner somehow. If Black plays at A (the safest move), white B, black C and white D will follow. This gives White a good result.

Diagram 6: This is another possibility for White. After black 3, white 4 aims at the tesuji of 8 before the move at 10, which makes it necessary for Black to capture two stones with 9 and 11. This gives White a better position in the corner compared to Diagram 4. White 12 helps his stones while attacking Black's marked stones. If Black plays at A, White will choose B. If Black plays at C, white A, black D and white E will follow.

Solution 1A: Last week's problem was what should White do after black 1. Connecting with 2 leads to the simple variation through 6. White gets a large corner, Black gets a group on the right side while capturing White's marked stone. The marked black stones are not completely dead yet. Black can use them to play at A or B.

Solution 1B: If he doesn't want to sacrifice his marked stone, White can also answer with 2. But after 3, white 4 is necessary unless White has a stone at A. Black captures a stone with 5 and 7 to get a large corner. This is not too good for White.

Solution 1C: If the marked stone is present, white 4 is a good move after black 3. Because White's position won't collapse after black A, white B, black C, white D, etc. through H, Black has to ensure life with 5. White should then capture black 1 with A.

Problem 1: This situation occurred in an actual game. How should Black respond after white 2? Find a reasonable sequence.

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Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.