Hex board game strategy

Question

I was teaching myself how to play the Hex board game by reading some books. I learned how to do 2x2 and 3x3 hex games by starting at the principal diagonal. I wanted to know what the winning strategy would be for player one (white) in a 4x4 Hex game starting from the principal diagonal.

Consider a 4x4 Hex.

Show that White has a winning strategy, starting anywhere on the principal diagonal that is in any of the hexagons 1,6, 11, or 16.

Here is what the setup would be:

Let the Hexagons be represented by numbers such as:

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

Let White have the first move. Let black have the second move.

White opens up at 6 (principal diagonal).

Answer 1

The winning strategy for such a small Hex board is shown in this basic strategy guide.

Like tic-tac-toe, on a 4x4 board white will always win by opening on the main diagonal, because for every counter that black can make, there is another way for white to force the win. Once white can form a "two-bridge" by placing the second piece in a non-adjacent space but with two empty neighbouring hexes in common, there is no way to block white from completing the chain, since there are two empty adjacent hexes to complete the link.

Here's an example position after white's second turn:

As you could see by playing out all the scenarios for white along the main diagonal, it's impossible to stop white from forming a "two-bridge"

• If white plays a1, there are two-bridges at b3 and c2. Black can't stop both.
• If white plays b2, there are two-bridge plays at a3, c4, d3, and c1.
• If white plays c3, it's a mirror position of b2.
• If white plays d4, it's a mirror position of a1.

Black can't win because there is always a way for white to orphan a black piece on this size board, making it impossible for black to form a "two-bridge".

I'm not that familiar with the game but my understanding is that the strategy only really becomes deep and interesting once the board gets to a 10x10 size.