The implications could be troubling, as Mulder shows. One idealistic young official of the League blithely wrote: “It is the starvation of the general population and in particular of the poorest people which is likely to cause such trouble in the aggressor country that it must give way.” No wonder that some Conservatives described the Leaguers as “bloodthirsty pacifists”. And liberal internationalists, who might previously have seen free trade as something benignly ­apolitical, now took the view that economics and politics could not be separated. Bizarrely, they were lining up with the nationalist ­German general Ludendorff (author of a book on “total war”), who had famously said: “Army and nation are one.”

We all know that the League of Nations failed miserably; so its great economic weapon was a dud. But here, too, Mulder shows that things were more complicated than that. The primary point of the weapon was deterrence, and in that capacity it did chalk up some successes. Admittedly, these involved relatively weak states: 1925 Greece invaded Bulgaria, after a Greek soldier chasing his dog across the border was shot by a Bulgarian sentry, whereupon the “War of the Stray Dog” was rapidly ended by the threat of sanctions.

The big failure was the handling of Mussolini’s invasion of Ethiopia in 1935. The League’s strategy was a bit too clever: concentrate on blocking Italian exports, and the lack of foreign earnings will bring the economy to a halt. Real damage was done, but not enough; and the selective bans on exports to Italy did not include oil – essential for both its economy and its army – because American companies were now major producers, and the United States was not in the League.

In a grisly paradox, Mulder argues that economic sanctions did have a huge effect in this period: they actually accelerated the move towards war. Mussolini became obsessed with a policy of national “autarky”, to guard against future measures. Hitler thought constantly about Blockadefestigkeit, “resilience against blockade”, eyeing from an early stage the rich farmlands of the Ukraine and the oil wells of the Caucasus. And Japan, a rising industrial power with very few natural resources of its own, went down the same path, grabbing large parts of the Asian mainland and, fatefully, making war on the US when the latter finally decided to cut off its oil supply.

I confess that if I had walked into a bookshop and seen a volume on the history of sanctions, I might not have glanced at it for long. How wrong I would have been. Some may read this book for its possible relevance today – though it will not have Mr Putin quaking in his boots, and in any case the story here ends in 1945. But taken as a superbly researched work of history, it lights up key aspects of the 20th century in a deeply thought-provoking way.

The Economic Weapon by Nicholas Mulder is published by Yale University Press at £25. To order your copy for £19.99 call 0844 871 1514 or visit the Telegraph Bookshop