He says that “one of the surest indications that war still has a future” is the lust for power shown by leaders of both past and present.
Mr Overy said: “Power works best as an explanation when history turns to the individuals who drove themselves to become the great conquerors, men whose raw ambition mobilised support from their people for unlimited conquest – Alexander the Great, Genghis Khan, Napoleon, Hitler. This is hubristic power based on arrogant self-belief and it usually evaporates with the death or defeat of the leader.
“But so long as they lead, and there are people willing to follow, war is unlimited and destructive on a vast scale. This is the most dangerous and unpredictable explanation for the persistence of warfare and it covers the whole historical record. It is one of the surest indications that war still has a future as well as a long past.”
He added: “The wars of the future draw on a grim heritage. The fact that peace would seem to be the rational option for most humans has never been able to stifle the urge to fight when it seems necessary, or lucrative, or an obligation. And that heritage is the chief reason it is possible to imagine a future war.”
In March, a group of former defence and security chiefs warned that the UK must start preparing for war.
Their report said: “To be credible in deterrence terms we need to prepare genuinely for war and communicate this to potential foes, NATO and allies, and particularly to the British public.
“We must signal to adversaries and potential adversaries the fact that we are strong and want to get stronger whilst at the same time having no interest in attacking or subverting any non-aggressive city or country.
“Our land forces and reserves could be said to have fallen far below national critical mass. This must be reversed and the relationship between size and technology must be better understood and articulated.”