Well, you may have read ivan37's write-up on the history of Hnefatafl and find yourself saying, "Yeah, well all that's nice, but how do you play it already?" As ivan37 correctly asserted, the rules to Hnefatafl were gradually lost as its popularity waned in the face of chess' ascension, but over the past century a number of scholars have been able to piece together what were probably the rules to the game. It should first be made clear that there were a number of variations in the original game, depending on where you were playing and who with. Think of it as rather like a game of pool - the "house rules" vary from pub to pub.
While one of the variations was the size of the playing board, the most common version of Hnefatafl was played on a 13x13 field, with the starting layout of the pieces being as follows:
---------------------------
| % - - - * * * * * - - - % |
| - - - - - - * - - - - - - |
| - - - - - - - - - - - - - |
| - - - - - - - - - - - - - |
| * - - - - - @ - - - - - * |
| * - - - - @ @ @ - - - - * |
| * * - - @ @ K @ @ - - * * |
| * - - - - @ @ @ - - - - * |
| * - - - - - @ - - - - - * |
| - - - - - - - - - - - - - |
| - - - - - - - - - - - - - |
| - - - - - - * - - - - - - |
| % - - - * * * * * - - - % |
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The * characters represent the attackers, and the @ characters represent the defenders. The K at the center of the board is the king. The object of the game for the attacker is to capture the king, and the object for the defender is to guide the king to escape. This is done by moving him to one of the four corner squares, also called king's squares, and represented in the diagram by % symbols. The center square, where the king is initially placed, is also a king's square (called the "throne" in some versions). The king obviously may not use this square to escape, but it does have some strategic value, which will be explained shortly.
All pieces in the game move as rooks in chess. That is, they may move as many spaces as they want in an unobstructed horizontal or vertical line. However, only the king may inhabit one of the five king's squares. The warrior pieces may pass over the central king's square if it is vacant, but none of them may end their turn there or on one of the corner squares.
The warriors of either side may be captured by "sandwiching" them between two opposing warriors, or between an opposing warrior and a king's square. The king acts as a warrior in this sense - sandwiching an attacker between a warrior and the king results in that attacker's capture. Following are some examples of valid captures:
--------- --------- --------- ---------
| % * @ - | % - - - | % - @ - | % - @ -
| - - - - | - - - - | - - * - | - - * -
| - - - - | - @ * @ | - - K - | @ * @ -
In each of the above examples, the attacker represented by the * symbol would be captured. However, the capture must have been initiated by the defender. In other words, if the attacker had moved between two defenders on his turn, that would not result in his being captured. In addition, a defender cannot be captured using the central king's square if that square is currently being occupied by the king. Note that multiple captures are possible - in the example on the far right, both attackers would have been captured, but only if the defender in the lower right corner had made the capturing move.
The king himself can only be captured if he is surrounded on all sides by hostile pieces or squares. All five of the king's squares are hostile to the king for these purposes. The following diagrams illustrate ways in which the king may be captured:
--------- | * - - - | - - - - - - - - -
| % K * - | K * - - | - - * - - - % - -
| - * - - | * - - - | - * K * - * K * -
| - - - - | - - - - | - - * - - - * - -
Most versions of Hnefatafl state that the attacker moves first, but there are a few which give that advantage to the defender. That's about it for the rules. As you can see, Hnefatafl is a fairly simple game to learn. However, the more you play it, the more complex it will become for you. One advantage which Hnefatafl has over chess is that the two sides, attacker and defender, have very different objectives. As such, different tactics are needed to achieve victory on either side.
As the attacker, you have the clear advantage of numbers. However, the mobility of the king on the open playing field, coupled with the fact that he has four avenues of escape, makes containing him a more difficult task than it may initially appear. Capturing the defender's warriors is key, but don't lose sight of your real objective. Use your warriors to form diagonal lines around the defenders. When properly sealed, these lines cannot be penetrated. Once you've achieved this, it's simply a matter of tightening the noose and eroding the defenders until the king can be captured.
The defender's advantages are already mentioned: strong mobility and several possible targets for escape. The key here is not to get yourself surrounded. Sacrifice is the byword of a successful defender. Do not hesitate to allow your warriors to be captured, especially if it distracts the attacker from his goal of cutting off your escape routes. Don't waste your moves capturing the attacker's pieces - every turn you spend fighting him is a turn you could have spent moving your king closer to escape. Once your king gets out into the open field, stopping him becomes exceedingly difficult. This isn't chess, and your king is no pansy. Use him or lose him.
The rules vary slightly in different versions of Hnefatafl, and a number of variants have been found with different board sizes as well. The Irish game Fithcheall was played on a 7x7 board, another Scandinavian variant called Tablut was played on a 9x9 board, and a Welsh variant called Tawlbrwdd was played on an 11x11 board. Modern games being sold as Hnefatafl or "The Viking Game" most closely resemble Tawlbrwdd in this respect. The "core" game of Hnefatafl was most often played on a 13x13 field. A later Saxon version entitled Alea Evangelii sported a 19x19 board. In each of these variants, initial piece placement varies slightly but follows a similar pattern to that shown above. The rules are also similar. For a more thorough discourse on the history of Hnefatafl and some of its variants, I encourage readers to visit http://user.tninet.se/~jgd996c/hnefatafl/hnefatafl.html. Some of these games can also be played online at gamerz.net and totalserve.co.uk.
And finally, for those of you wishing to pronounce Hnefatafl correctly, try saying "nef-tahl". Now try saying it while exhaling through your nose during the initial "n" and adding a slight schwa sound between the "h" and "l" at the end. Now do it while standing on your head. Now you look silly and sound silly, but at least you're saying Hnefatafl right ;)