Viking Chess

How Viking Chess works

Viking Chess, properly called Hnefatafl, is an asymmetric siege. You command the defenders: a small band of soldiers guarding the king, who begins on the central throne. The computer plays the attackers, roughly twice as numerous, ringed around the edges of the board. Every piece moves like a rook in chess, sliding any number of empty squares along a row or column, never diagonally and never through another piece. You win by walking your king to any corner square; the attackers win by surrounding the king on all four sides.

Captures are custodial. Sandwich an enemy piece between two of your own along a row or column and it comes off the board. The trap only springs when the opponent moves in to complete the sandwich, which produces the rule newcomers always miss: stepping voluntarily into the gap between two enemies is completely safe. You can slide a soldier right between two attackers, sit there untouched, and carry on next turn.

Playing the outnumbered side

Two-to-one odds sound grim, but the arithmetic quietly favours you. The attackers need most of their army intact to do their job, because sealing off all four corners takes a wall of pieces, and no reinforcements ever arrive for either side. Every even trade weakens their blockade more than it weakens your escort. So don't hoard soldiers; spend them on captures that punch holes exactly where you intend to run.

The standard winning pattern is a fork between two corners. Lean on one corner until the computer commits pieces to walling it off, then switch wings and press a second corner on the far side of the board. Every attacker that shuffled across to plug the first gap is an attacker missing from the second, and patient switching stretches the ring until it snaps. Only then does the king move. Bring him out early and he becomes the target of every piece on the board; bring him out last, down a cleared lane with an escort on each flank, and the run itself is two or three quiet moves.

What the computer is trying to do

The attackers' plan is a closed ring a square or so off the edge, tightened until no lane is left. Knowing that tells you when to hurry. Harass the cordon before it settles, because every captured attacker leaves a permanent gap. Watch for the ring leaning toward one side of the board; that is your cue to play on the other. And never let the computer shepherd your king back toward the centre, where there is space to close in on all four sides. In the final stretch an escort matters more than a capture: a king with a friendly soldier on one flank simply cannot be enclosed from that direction.

Habits that win games

• Threaten two corners at once; the attackers cannot wall off both, so one route stays open.
• Trade freely when the exchange is even; the blockade needs numbers more than your escort does.
• Clear a protected lane first and move the king late, never first.
• Use custodial captures to thin the wall exactly where you plan to break through.
• Step between two enemies without fear; capture only happens when they move in to flank you.

A thousand years of tafl

The tafl games were the strategy games of northern Europe for the better part of a millennium, played across Scandinavia, Britain, Ireland and Iceland well before chess arrived. Boards and pieces have come out of Viking-era graves and ship burials, a famous wooden board was dug from an Irish crannog at Ballinderry, and a twelfth-century Earl of Orkney, Rognvald Kali Kolsson, put tafl first when he listed his nine noble skills in verse. Hnefatafl means roughly the king's table.

Chess spread north around the eleventh and twelfth centuries and slowly pushed tafl out, and the original rules faded with it. What survived did so almost by accident: in 1732 the botanist Carl Linnaeus watched the Sami playing a 9x9 version called Tablut on his Lapland journey and recorded the rules in Latin, and a later English translation garbled enough details that early revivals played badly unbalanced. Modern reconstructions such as Fetlar and Copenhagen Hnefatafl restored a fair fight, and the family still spans the small Irish Brandub at 7x7, the Welsh Tawlbwrdd, and the enormous Alea Evangelii, laid out on a 19x19 grid in a medieval English manuscript. The duel you are playing here is a genuine thousand-year-old design, and it still bites.