Tackling Central Draw Forts

Wednesday, 2nd March 2016

Draw forts can be a big problem in serious hnefatafl play on boards of 11x11 squares upwards. A draw fort is a construction of pieces generally useful to the king's side. A typical draw fort has an impregnable outer shell of defenders, with space inside for the king to move safely back and forth.

Draw forts are an instinctive strategy for a defending player who considers their position lost. This can happen often in a game like The Viking Game or Fetlar hnefatafl, when the attacking player has learned the strategy of blocking the corner exits quickly but the defending player has not yet learned to counter this.

In casual games the problem is not too serious. But in tournament play it can be disastrous. Consider an average but devious player outmatched in general strategy by a former champion in the early rounds of a tournament. The devious player could avert the expected loss with a blatant spoiling strategy: construct a draw fort within the first few moves and nudge the king back and forth within it till a draw is declared.

There have been various attempts to counter this behaviour over the years. One simple proposal is that if the game is brought to a standstill by repetition, the king has lost, because he is never going to escape. He is unable to leave the battlefield and is effectively captured already. But this rule also rules in the attackers' favour if the king is in a strong position able to switch between two threats ad infinitum. This unintended consequence may have an effect on the balance of the game.

A more successful attempt to eliminate a blatant spoiling strategy is to award victory to the attackers if they completely surround all of the defending pieces. This was a feature of York Hnefatafl in 1980, and was revived in Copenhagen Hnefatafl.

Another idea against blatant spoiling strategies is that a draw can only be awarded if the game has been advanced to a certain stage, say a certain number of captures on each side. This has been used at Aage Nielsen's web site for games other than Copenhagen hnefatafl.

I think that the best solution is the one from York Hnefatafl: if the defending pieces are completely surrounded then they have lost, as they and their king are confined. This has the added bonus of elminating a long drawn-out end game against a novice or computer defender, where the attacker has to gradually constrict the defenders and pick them off one by one.