Nine Men's Morris Problem

Wednesday, 17th September 2014

This is the first in an occasional series of problems for the game of nine men's morris. Feel free to leave your proposed solution in the comments, or on one of this site's social media accounts (see buttons in the footer), or alternatively, by email.

In this puzzle it is white's turn to move. The notation indicates the first and last point numbers on each row. Notice the running mill on points 4-6 and 13-15 which has reduced black to four pieces. From this position, only one move will guarantee white a victory in three turns: what is it?