Hugh Pickens writes: "Nature reports that data collected on the timing of attacks and number of casualties from more than 54,000 events across nine insurgent wars, including those fought in Iraq between 2003 and 2008 and in Sierra Leone between 1994 and 2003 suggests that insurgencies have a common underlying pattern that may allow the timing of attacks and the number of casualties to be predicted. By plotting the distribution of the frequency and size of events, the team found that insurgent wars follow an approximate power law, in which the frequency of attacks decreases with increasing attack size to the power of 2.5. That means that for any insurgent war, an attack with 10 casualties is 316 times more likely to occur than one with 100 casualties (316 is 10 to the power of 2.5). "We found that the way in which humans do insurgent wars — that is, the number of casualties and the timing of events — is universal," says team leader Neil Johnson, a physicist at the University of Miami in Florida. "This changes the way we think insurgency works." To explain what was driving this common pattern, the researchers created a mathematical model that assumes that insurgent groups form and fragment when they sense danger, and strike in well-timed bursts to maximize their media exposure. Johnson is now working to predict how the insurgency in Afghanistan might respond to the influx of foreign troops recently announced by US President Barack Obama. "We do observe a complicated pattern that has to do with the way humans do violence in some collective way," adds Johnson."