On the psychology of defence


There are two bits of Clausewitz (just two?) that have long puzzled me. The first is where he says that a statesman should know what sort of war he’s embarking on, before getting into it. In modern times, that line has often been contrasted with John Reid’s unfortunate quote about Helmand, in which he said the British would be perfectly happy to leave without having fired a shot. The second is where Clausewitz argues that the defence is stronger than the attack.

I still don’t understand the first. Prediction in complex social systems is impossible – and any foresight more a matter of chance than genius. Philip Tetlock gets into that in his last two books – on the value of expert political judgment (negligible) and the possibility of ‘superforecasting’. If we read Clausewitz’s remark as a cautionary note against overconfidence, then fair enough. But retrospectively expecting elites to have a firm grasp on the character of a future war seems a bit unfair. Strategy is in part improvisational; responding creatively to the unexpected in situations that are always in flux.

On the second bit of Clausewitz, I have an answer! For the real aficionados, the full paper, presented at the ISA conference this week, is online here. The short answer is here – and it comes with a heavy dose of psychology.

In brief, I argue that Clausewitz is right, and that Daniel Kahneman and Amos Tversky’s Prospect Theory can help us see why. This theory suggests we are profoundly loss averse. We are prone to gamble more when we perceive ourselves to be losing than we would if winning. You can demonstrate this very neatly in lab based psychology experiments which set up precisely the same (cash) payoffs and probabilities associated with two scenarios, but depict one scenario as the choice between a gamble on avoiding a loss, or the acceptance of a certain, but smaller loss; and the other scenario as a gamble on a large gain, versus the possibility of a smaller, but certain gain. We tend to gamble in the loss scenario, but not in the gain.

Why? A bird in the hand is worth two in the bush. Evolutionary psychology provides a compelling rationale – in marginal environments, where survival is rather finely balanced affair, losing valuable resources could be disastrous; but at the same time it is profoundly dangerous to risk everything on the possible acquisition of new resources. And so in ‘wars’ between groups of chimpanzees overwhelming odds are required before the chimps will attack. The tactics of raid and ambush are favoured over pitched battle – as they often are in wars between hunter gatherer communities.

Some important caveats: In the real world, of course, the payoffs and probabilities associated with them are rather messier than in the psychology laboratory. That’s certainly true in war, as Clausewitz noted with his extensive discussion of uncertainty and chance. There are also plenty of real world examples of attack dominating defence, in battles and campaigns alike. How are we to square this with Clausewitz’s assertion? It’s hard to control for the many particulars of historical examples – terrain, technology, numbers, cohesion and so on. Sometimes it’s hard even to know which is the attacking force, and which the defender, as attacks culminate, and defence gives over to the counter-attack.

Fair enough. And yet, at some meaningful level of abstraction, Clausewitz’s remarks chime with Prospect Theory. In a struggle for possession (Clausewitz thought mostly about possession of territory, but there may be other plausible currencies in which to measure appetite for risk), there is a tendency to gamble in order to avoid the prospect of losing. The attacker, meanwhile, will be increasingly reluctant to gamble on marginal gains, especially if his initial objectives have been satisfied.

What we have, we hold.

For more on Prospect Theory, check out Daniel Kahneman’s excellent popular psychology book, Thinking Fast and Slow.

Image via flickr.

One thought on “On the psychology of defence

  1. With respect to a statesman’s role in understanding the character of a particular war, I think that Clausewitz explains this in some detail with Chapter 2 of Book 1, “Purpose and Means in War.” He recognizes that “political objects can greatly alter during the course of the war and may finally change entirely,” but a statesman should still examine initial probabilities from the perspectives of both sides to determine if victory is possible and at what cost: “Once the expenditure of effort exceeds the value of the political object, the object must be renounced and peace must follow.” Prudent statesmen must consider the full range of actions that might constitute political success short of the complete defeat of the enemy’s forces and breaking their will to fight.
    There is also a tie-in with Prospect Theory, to the extent that Clausewitz hinged all deliberations on probabilities and said that “the very faintest prospect of defeat might be enough to cause one side to yield.”


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s