In 1909 the British empire was locked in a frantic race with Germany for naval military supremacy. The continent was carved into antagonistic power blocs of states and kingdoms, jealous of each others' colonies. The atmosphere was thick with anticipation of a major new European conflict.
In that year, a Labour Party MP and journalist Norman Angell came to the rescue, with a pamphlet designed to put this febrile talk of European war to bed. Angell's thesis was that the cost of a general war to the European economy was so manifestly enormous that it was highly unlikely to happen - and, if it did, would be soon over. The economic self-interest of nations - of the individual citizens and businesses in them - would block military conflict.
"What is the real guarantee of the good behaviour of one state to another?" Angell asked. "It is the elaborate interdependence which, not only in the economic sense, but in every sense, makes an unwarrantable aggression of one state upon another react upon the interests of the aggressor."
Angell's pamphlet was a bestseller. It was bulked out into a book called The Great Illusion, which was widely translated and published around the world. Its thesis was, of course, just about as misleading as any book's has ever been, either before or since.
We stand in the middle of Angell's ashes today as we mark the hundredth anniversary of the end of the First Word War. Ten million soldiers and ten million civilians died between 28 July 1914 and Armistice Day, 11 November 1918. Economic self-interest did not save them.
A chapter by David Jacks, part of a new book released last week on the economics of the Great War, shows that the shadow of the conflict was enormous. The arteries of global commerce were thoroughly ruptured in 1914. World exports did not return to the pre-1914 growth path until the 1970s.
The extreme economic dislocation that followed the end of the First World War arguably prepared the ground for the Great Depression, mass unemployment and the rise of fascism that culminated in the Second World War.
The counterfactual question of how the lives of our great-grandparents, grandparents - indeed all of us born over the past 120 years - might have been different if the nations of Europe had not slithered over the lip of the cauldron of war in 1914 is mind-meltingly large. The lesson of Angell's error is, of course, that no forecast of how nations will behave can rest solely on an analysis of economic or commercial interest. But it's a lesson that we still find it a hard to absorb.
Sometimes we hear that a no-deal Brexit, which leads to us crashing out chaotically from the European Union next March, is most unlikely because it would plainly be economically destructive for all involved.
British firms understand it. European firms grasp it. The majority of MPs don't want it. Ergo, it's really not going to happen, however much it gets talked up. But accidents do happen. And especially in complex, yet fragile, geopolitical environments.
AJP Taylor has fallen out of fashion these days. But he was the first popular TV historian. And in the 1970s he enthralled British viewers (speaking to them plainly without notes and without sophisticated production techniques) of his theory of the causes of the First World War. According to Taylor, the military powers in 1914 were tightly constrained by the practical logistics of moving soldiers and supplies around the continent by railway.
"All the mobilisation plans had been timed to the minute, months or even years before and they could not be changed. Modification in one direction would ruin them in every other direction…. Any alteration in the mobilisation plan meant not a delay for 24 hours but for at least six months before the next lot of timetables were ready."
These constraints, according to Taylor, meant that a single spark - the assassination of an Austrian Archduke in Sarajevo - exploded into a wildfire; this was "war by timetable".
Maybe, maybe not. Historians have been debating the causes of the First World War ever since it ended and have been unable to settle on a consensus.
Yet when we think about Theresa May's decision to trigger Article 50 in March 2017 - setting the twoyear countdown running on our exit from the European Union - before she had even reached agreement within the Conservative Party, let alone the country, over what sort of post-Brexit vision to pursue, it is hard not to hear disturbing echoes of the Taylor thesis of calamity by timetable.
It's hard not to be reminded of how potentially dangerous are those leaders who have painted themselves, and their countries, into a corner.