Edge template V1a

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Template V1-a is a 5th row edge template with 1 stone.

This template often appears as a third move, for instance in the a3 opening, because the played piece is guaranteed to link to one edge and is not too far from the other one. Thus it follows the principle of the weakest link.

Note that there is also a mirror image form of this template.

It may seem that this template is very strong because it reaches 5 rows into the board, but it rarely occurs outside of the opening, because of the huge size of the template; the template requires 31 empty hexes and 10 hexes along an edge — the entire edge on the 10x10 board!

Furthermore, the large perimeter makes it more vulnerable to encroaching adjacent plays and forcing moves. Additionally, the carrier surrounds the 5th row piece on both "shoulders" so that non-overlapping plays from the 5th row piece can occur in only two directions.

Defending the template

Red's threats

Reductions to a ziggurat:

Reductions to template IVa:

Reductions to template IVb:

Reduction to template III-1-b:

Blue's options

These threats only overlap in 3 hexes, so to attempt blocking the template, Blue must move in one of these.

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If Blue moves at x:

Red responds as follows.

12

Red is threatening to connect at "+". Blue must block by playing somewhere between Red's two pieces. Red then continues as follows:

3416527

Red has forced a bottleneck, resulting in a 2nd row ladder. Red's 2 acts as a ladder escape. The final position is

34165210897

If Blue moves at y:

Red can respond at 2, which is connected to the bottom and forms a loose connection with the Red piece on the 5th row. To stop the immediate connection, Blue must play at a or b.

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If Blue moves at a, Red connects via edge template IV2p.

4321

If Blue moves at b, Red connects via edge template IV2a.

4321

If Blue moves at z:

The situation is entirely symmetric to when Blue moves at y. Red can respond at 2. To stop the immediate connection, Blue must play at a or b.

ab21

If Blue moves at a, Red connects via edge template IV2p.

3421

If Blue moves at b, Red connects via edge template IV2a.

4321