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: 

Black on the move wins in 5 moves, thus: 

(1) 16-19 27-31 (2) 20-24 32-27 (3) 28-32 27x20 (4) 19-24 20x27 (5) 32x23

and White is pinned.

With three Kings against four a player can sometimes offer prolonged resistance.  But finally the stronger player will always be able to force an exchange which secures the victory.  In the position of Diagram 92 for instance Black will proceed as follows: 

          (1) 18-15 19-24

It would not help to play 27-24, as Black would reply 14-17 and exchange on the next move by 10-14.

          (2) 11-16

limiting White’s mobility.

(2) ... 23-26

In answer to 24-20 Black would play 15-19.

(3) 16-19 24-28 (4) 14-18 26-30 (5) 19-23 28-32 (6) 15-19 27-31

32        31        30
+---------------------------------------+
|    |    |    |    |    |    |    |    | 29
|---------------------------------------|
28 |    |    | oo |    |    |    |    |    |
|---------------------------------------|
|    |    |    | oo |    |    |    |    | 21
|---------------------------------------|