This history identifies international economic sanctions as a central and understudied innovation of interwar internationalism. Sanctions were initially conceived by the victors of World War I—principally Britain, France, and the United States—as an ‘economic weapon’ inspired by new techniques of blockade and economic warfare developed in 1914-1919. Enshrined in Article 16 of the Covenant of the League of Nations, sanctions entailed the coercive economic isolation of countries that violated peace treaties. Sanctions were novel because they were a form of economic pressure imposed against civilian populations in peacetime and internationally legitimated as punishment for the crime of aggression—a break with preceding centuries in which such acts of economic isolation were only allowed in time of war. The study clarifies the differences between sanctions as they emerged in the early twentieth century and other forms of economic pressure—embargoes, (pacific) blockades, boycotts—and recovers the meaning and agendas behind sanctions as argues that the wartime origins and coercive nature of sanctions were widely recognized by their advocates and critics alike, and that this recognition persisted deep into the 1920s and 1930s, when the discourse of international blockade and economic weaponry was slowly displaced by the more neutral language of ‘sanctions’ and ‘collective security’.

It demonstrates that the most popular political and strategic theory of sanctions was one which conceptualized them as a deterrent: sanctions were thought to be capable of keeping the rulers and populations of other states peaceful by threatening them with quick and universal material devastation if they transgressed international rules. It emphasizes how the introduction of economic sanctionsentailed a revolution in international law, ending the centuries-old concept of neutrality: to effectively isolate aggressors, interactions with neutral countries had to cease, and impartiality was delegitimized. In the following pages, a new interpretation of the international political, economic and military crisis of the 1930s is developed which centers around the role of sanctions as an instrument of deterrence in an interdependent world economy. While the rapid advent of sanctions meant that many countries were materially and politically not quite prepared to implement them, the discourse of the economic weapon become very strong and feared, partially by reviving memories of the power of blockade in WWI.

The existence and threat of sanctions was therefore an unintentional stimulus to autarky, and a factor which accelerated attempts by Nazi Germany, Fascist Italy and militarist Japan to aggressively challenge the interwar order. Finally, this analysis considers sanctions as a form of politicization of the early twentieth century world economy. It recovers the forgotten interwar history of the ‘positive economic weapon,’ a mirror image of the negative instrument of sanctions that focused on provision and resource mobilization instead of deprivation and interdiction. It shows how attempts to construct this financial instrument against aggression failed in the 1920s and 1930s before appearing, in a different guise, in the form of Lend-Lease, during WWII, and how this material support function improved the appeal of internationalist institutions after 1945. Altogether, this work situates the birth of economic sanctions in its political, material, legal, theoretical and strategic context, helping us understand why these measures inspired by economic total war against civilians survived far beyond WWI into the twenty-first century, where they continue to form a prominent part of international affairs.