Wars and volcanoes have much in common. Making predictions about a coming war can be likened to a volcanologist predicting how a volcano will behave if it erupts.
There are usually lots of warning signs that a volcano is about cook off: Small tremors, rumblings deep within the earth, more fumes and vapour, the sudden melting of snow caps, and so on. Based on experience and known facts, volcanologists can make educated guesses about how the eruption might unfold, but they have been known to make significant errors and some variables will always be difficult to anticipate.
