DIAGRAM 90.
If it were White's move, Black would easily win; for after (1) …, 27-32; (2) 19-24, 9-5; (3) 10-6, White cannot avoid the exchange. For instance: (3) …, 5-1; (4) 24-19. The problem reduces itself therefore to changing the move from Black to White. This is accomplished by:
Black White
(1) 15-18 27-32 (2) 19-24 9-5 (3) 10-14
Threatening 24-27. White can only reply
(3) … 32-28 (4) 24-27 5-1 (5) 14-9, etc., as above.
If the weaker side does not control both double corners the exchange can be forced much more easily, as an experiment will quickly show.
32 31 30
+———————————————————-+
| | oo | | | | | | |29
|———————————————————-|
28 | ** | | oo | | | | | |
|———————————————————-|
| | | | | | | | |21
|———————————————————-|
20 | ** | | | | | | | |
|———————————————————-|
| | ** | | | | | | |13
|———————————————————-|
12 | | | | | | | | |
|———————————————————-|
| | | | | | | | | 5
|———————————————————-|
4 | | | | | | | | |
+———————————————————-+
3 2 1
DIAGRAM 91.
Sometimes the stronger side has an occasion to give up two Kings for one thereby forcing a position similar to that of Diagram 88. Diagram 91 offers an example: