Black had 2
possibilities that could not be countered without creating another possibility: c7-c5 and e8. With 1.c1-h3 White blocked these two ways out with one single move. Some of
the possible attempts and the respective counters:
- if 1.
… c7-c5, then 2. i2-g4;x - if 1. … e8, then
2. a4-d4 - if 1. … a1-c3, then 2.
a3-c5 - if 1. … i1-e5, then 2.
f8-f2 - if 1. … g6, then 2.
i4-g4 - if 1. … i4-g4, then 2.
c7-c5;x
(1.
h3 would not have worked. It blocks the c1-i3 line, which gives Black
another chance: 1. … a4-d4 - and a
sure capture on either the d1-d8 line or the b1-i4 line.)