Gwynne Dyer: Out of blue - bang! - war

"If they are not remembered, was the sacrifice they made even worthwhile?" asked an American veteran of the Iraq War who named his son after a fellow soldier who was killed there.

That's quite common, actually. My brother-in-law is named after a member of his father's bomber crew who was killed over the Balkans in 1944. But World War II is still just within the reach of living memory.

We have just been asked to commemorate the 100th anniversary of the end of World War I. That is no longer memory; it is history. The images are familiar and some families have names and even pictures of relatives who died in the war, but very few people now alive ever knew them personally.

So how should we commemorate the war? There's not too much rhetoric about glory any more, thankfully - we have grown up a bit - but a lot about sacrifice. That's a safe subject, although the majority of the soldiers who fought in the war had no choice about being there.

Just under the surface, however, almost everybody now realises that World War I was a huge, pointless waste of at least 16 million lives.

Many people knew that even at the time. Yet nobody knew how to stop it at the time, and we in the present don't really know what to say about it.

The best use of the brief interval of contemplation about war on November 11, therefore, was to try to understand what kind of phenomenon it was. Starting with a simple question: where does war come from? The answer is equally simple. Human beings didn't invent war; they inherited it.

Our branch of the primate family has always fought wars. If there is an original sin, it goes back beyond the time when the chimpanzee and human lineages split five million years ago. (Chimpanzees still fight wars too.) So forget about the "causes of war" in the history books. Every kind of human society, with every imaginable kind of economy, has fought wars.

Second question. How did war get so big? World War I and II were far more destructive than previous wars, and World War III (if the Cold War had ever turned hot) would have been at least 10 times bigger than that.

When the size and resources of a society grow, it tends to fight bigger wars just because it can. The issues at stake are not bigger than before, but losing a war is so unappealing that countries generally won't quit until they have thrown all their resources into it.

And finally, how can you tell when some stupid little thing such as an assassination in Sarajevo is going to blow up into a "world war" with all the trimmings? Answer: you can't. Which brings us to the Power Law.

People want a big disaster to have a big cause and a recognisable villain, so people writing about the outbreak of World War I try hard to find some country to blame. If they are writing in English or French they generally blame Germany, which allegedly wanted the war and made it happen. But that's nonsense.

The Power Law describes how so-called "critical systems" like those that produce earthquakes and forest fires absolutely do not discriminate about the scale of the event.

Most events will be on the smaller side, but you don't need special causes to get a huge one: literally any size of event can happen at any time.

A critical system is one that is inherently unstable, and locks in more and more instabilities as time goes by.

Think of the accumulating stresses along a fault line between two continental plates, or the accumulation of inflammable debris on the forest floor. From time to time there will be earthquakes and forest fires, but most of them will be small. The Power Law says that any one of them could be the Big One.

To know if a particular class of events is subject to the Power Law, you just graph the scale of the events against their frequency. If it turns out to be a straight relationship where doubling the size of the event decreases the frequency by half - or makes it four times less likely, or 16 times, or any other power of two - then you are dealing with a critical system.

In that case, you can forget about seeking major causes for bigger events. A random pebble is 16 times less likely to cause a huge avalanche than a little avalanche, but it can cause either.

Jack Levy, in a massive 1983 study entitled War in the Modern Great Power System, measured the size of every war in the past 450 years by its casualties, and found that doubling the size exactly halved the frequency.

This means that great wars do not need great causes. Once sufficient strains have accumulated in a critical system, a world war can strike out of a clear blue sky, as it did in the summer of 1914. Or now, for that matter.