Tablut, a Viking board game
Tablut is a game for two players, Swedish (white) and Muscovy (black). Sweden wants their king to escape from the middle. The Muscovites want to stop him.
The Muscovite forces begin in their base camps, the darker squares at the board's edges. The Muscovites can move about within the base camps, but once a piece leaves, it is unable to return. The centre square, where the king begins, is the castle. No other piece is allowed to enter this square and once the king leaves, he cannot return.
All pieces can move any number of squares in a straight line vertically or horizontally, like rooks in chess. Pieces cannot jump over other pieces, the castle or the base camps. Each player can move one piece per turn and Sweden starts.
A piece is captured when it is sandwiched by two enemy forces along a row or column. Alternatively, a piece may be squashed between an enemy and restricted area. Pawns are only captured when it is the enemy's move that completes the trap: pieces are able to move safely between two stationary enemies. Once a pawn is captured, it is removed from the game. The king is harder to get hold of, in that he cannot be caught between an enemy and a restricted tile.
A Swedish pawn standing besides the king can be seized if both pieces become trapped. Suppose the royal pair are next to a Muscovite or restricted area, and another Muscovite pawn moves besides them in the same row or column. In that case, the Swedish pawn would be captured but the king would not be.
When the king has one unimpeded route to the edge of the board, the Swedish player warns his opponent by saying "raicki". When the king has two free ways, he says "tuicku", which is the equivalent of checkmate. Because computers are so ruddy marvellous, this will happen automatically. It's probably just as well because I doubt either of us knows how to pronounce the Saami words correctly.
Tablut is just one descendent of hnefatafl, a game played in the middle ages throughout the areas under Scandinavian influence. After the Vikings faded into the mists of time, the rules became obscure leaving little for nineteenth century experts to reconstruct the games from. There is evidence of similar tafl games played in other areas such as tawl-bwrdd in Wales, fidchell and brandub in Ireland and alea evangelii, the game of the Gospels, in England. These all centred around a king escaping from an attacking force but featured different numbers of pawns on differently sized boards.
While no complete and unambiguous description of a tafl game exists, Tablut is the best documented. Carolus Linneaeus, he of binomial taxonomy fame, observed the game being played during his travels among the Saami people in the far, far north in 1732. He tried his best, but didn't understand the locals' non-indo-European language, and so had to infer the rules from what he saw.
Finally, Linneaeus wrote that the king can only be captured if surrounded on all sides, rather than just two. I chose not to include this rule because it is reported to make the game rather unbalanced in favour of Sweden and other accounts of tafl games make no mention of it. If you feel particularly strongly about this, why not get in touch?