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

In this situation, there are only 3 possible winning moves for Red, and they are "a", "b", and "c". Of these, "a" is the easiest to verify, so we will assume Red plays there.

Before continuing the analysis, we first note that Red can escape all 2nd row ladders coming from the left, as follows:

Apart from attacking the bridge, which Red defends, Blue's next move must be in the blue area, or else Red plays at d and connects.

If Blue plays at c, e, h, or j, Red responds at d and gets a 2nd row ladder, which connects. If Blue plays at b, Red plays at x and connects by edge template IV1a. If Blue plays at d, Red plays at x and gets a 2nd row ladder, which connects. This leave a, f, i, g, k. To be continued.