Template VI1/Intrusion on the 3rd row

This article deals with a special case in defending against intrusions in template VI1, namely the intrusion on the 3rd that is not eliminated by sub-templates threats.

Basic situation

Red should go here:

The Red 1 hex is connected to the bottom, and threatens to connect to the top through either one of the "+" hexes. Thus these are the only important incursions. An incursion to the right of the number 1 hex is important only in connection with the two indicated here, and will be seen in the treatement below transposed into the sequel.

Third-row followup: i4

Figuring out the Must-play region

Red threatens to play at "+" points above, with these templates:

Edge template IV1a

We need only consider the intersection of these templates.

Incursion at j5

Incursion at j6

Incursion at h7

Third-row followup: j3 (stub)