Tower Defence: a Tactic in Hnefatafl

Saturday, 5th September 2015

For at least a decade, the tactics page on this web site has contained three tactics taken from chess: the fork, the pin and the forced move. But there's an interesting tactic not taken from chess. Four allied pieces in a square give an invincible formation, with no single piece being vulnerable to capture.

Called the "tower" by hnefatafl strategist Tim Millar, this immovable construction certainly feels like one. The fact that it is formed of warriors and not stone detracts from the analogy, but unlike the shield wall formation there is no good example of this tactic from the warfare of Vikings or their contemporaries. Later armies had the square formation, while earlier armies had the testudo, both of which reflect hardy formations of troops.

In fact the testudo brings us neatly to the possible inheritance of the tower from Roman games, and the Greek games from which they were derived. While the true rules for the game ludus latrunculorum are lost, the method of capturing pieces which it bequeathed to hnefatafl make the tower a very strong tactic in the former game. Given that ludus latrunculorum emphasises capture of enemies, it is even more relevant to that game than to hnefatafl, in which it is merely occasionally useful.

This is probably because the tower is a static formation. As soon as one of the pieces moves, the force becomes vulnerable to attack. Unlike a blockade, for example, it is impossible to move the tower without dismantling it. Despite its siege-like appearance, hnefatafl is a dynamic game in which the action must move about.

The king's side will use the tower most often. As they are surrounded at the start, the tower is a good defence against a closing blockade. Its invincible nature allows any piece behind enemy lines to make real threats against the attackers should any come into contact with the tower. And if the king is in a tight spot, his forming a tower in concert with three defenders will keep him safe while other allies harass the attackers to help him break free.

The tower is less useful to the attackers, but it might still be of benefit. If a defender threatens to escape from a blockade, or has already done so, a tower formed along the threatened edge of the blockade can protect the attackers on that side.

So while the tower is not particularly common in hnefatafl, it should still be part of a player's arsenal - knowing when it would be useful, and developing tactics to neutralise it when the opponent makes use of it.