Hnefatafl - the Viking Game

How pieces DON'T capture...part 4

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Although a warrior is captured by becoming trapped between two enemies, it is quite safe to move into a gap between them, as in this diagram. The white warrior can safely move into the gap, and is not captured. However, if one of the black warriors moves away, and then on the following move, it moves back, the white piece would then be captured. It is also safe to move into the gap between an enemy piece and one of the refuge squares.