Elementary Chain Counting Problems
Elwyn R. Berlekamp · 2000
The only way to stop the side chain is to sacrifice now. Even if A countersacrifices, we’ll get one chain in the west. Then B keeps control only by sacrificing 2. A eventually wins 5-4. 9-6 11-4 13-2 A ensures two chains total by looping the north to prevent a third chain there.