Fear agentsIn the March of Folly that is our human engagement in fighting wars, we have rather forgotten the importance of climate. While British troops used to say that a place was "hotter than Basra" – and are no doubt saying so again in a week where daytime temperatures reached 60 degrees C – it is still possible to keep fighting. Logistics teams keep air conditioning operational, and machinery functioning. Although apparently sometimes only just.

600 years ago no commander dreamed of trying to keep an army in the field outside the regular fighting season, mostly spring and summer in Italy. Of course this effectively destroyed growing seasons and exerted huge pressure on the citizens of besieged cities. Nevertheless, when the rainy season hit our Datini in October, they at least could get out to the farms to gather chestnuts and repair walls. Money was flowing again, and merchandise. Thus you could maintain enough economic activity for a war to be sustained. And war was in fact a desirable profession, especially for the younger sons of noble families who would not inherit.

Withdrawing from the field at agreed times not only gives the revenue generating civilian population a chance to regroup. It also gives the power brokers a chance to negotiate a peace or a truce. So, war could seem like reasonable way to get an advantage.

But, in our own time, we commit ourselves to continuous battle with no rules for relief or release. War is an old-fashioned way to solve a problem.