The Knight’s move in chess has often been the subject of investigation by mathematicians and a variety of theorems have been formulated, just as in geometry. Here is one of them. The minimum number of knights that can be placed on an 8x8 board, so that all unoccupied squares are attacked by at least one Knight, is 12. The solution is above. This week’s puzzle is tpo find the minimum for the 9x9 board, which is also unique.