Hnefatafl

Hnefatafl ("the king game") is an ancient boardgame played by the Vikings to pass the time on their ocean voyages. It was probably derived from a Roman game with similiar rules and was later adopted by the Saxons. A number of different boards have been found in Viking burial mounds and there was some variations in the rules as well.

The board is an 11 by 11 grid, the centre square of which is the throne. The defenders (black) are the Vikings, trying to get their king to the safety of the perimeter squares. The attackers (white) are whoever the Vikings were fighting at the time(!) - their aim is to capture the king.

All pieces move horizontally or vertically over any number of empty squares, except the king, who can only move up to three squares. No piece can move diagonally, and no piece except the king can move onto or through the throne square.

Captures are done by flanking the opposition piece with two of your own - note that multiple captures are possible. However, you may safely move a piece between two enemy pieces. Once captured, a piece is removed from the board.

The capture of the king is slightly different, in that he must be surrounded on all four sides by white pieces - or when his only escape is to the throne square. The king cannot assist in capturing opposition pieces.

White should cover the exposed corners while gradually advancing on all sides. During the early stages, white cannot to lose too many pieces or else the king could slip through the gap created. Later, exchanges of pieces are safer for white (who initially outnumbers black 2:1) but generally, the more pieces on the board, the harder it is for black to move his king about. Note that most attempts to storm the centre are easily defeated by black.
Black should try to keep white off-balance by switching the directions his king is trying to escape in.