To expound the law relating to war was a primary purpose of Hugo Grotius in the writing of his famous treatise, De jure belli ac pacis (1625). In Grotius’ opinion, a ‘very serious error’ had taken hold of the popular mind, to the effect that there was no law regulating the manner in which the combatants went about their deadly business. The events of the Thirty Years War, raging in central Europe at the time the book was written, could easily have given rise to such a notion. Be that as it may, one of Grotius’ central concerns was to refute this pernicious misconception. Even in time of war, he insisted, the opposing sides remain part of a common moral community, governed by the general law of nature, and also by the body of customary and contractual law known as the law of nations.

This chapter concentrates on the early months of the war, and delving into autobiographical testimonies looks more closely at the suffering and fate of enemy aliens. The chapter then describes the implementation of the policies adopted in the early months and deals with expulsion, forced repatriation and deportation. It then addresses the internment of civilians, which was one of the major novelties that the belligerent countries introduced in the European war. The chapter follows the spread of concentration camps throughout Europe and the British and French Empires, the internment gender and generational dimensions, and the beginning of the humanitarian activities that the mass internment of enemy aliens triggered. The third part of the chapter deals with another crucial novelty that concerned the property rights of the enemy aliens. States at war sequestered and confiscated their assets as part and parcel of the economic war they waged. The internment and sequestration of enemy property led to enormous growth in the apparatuses of the state. And this meant that state involvement in the lives of civilians increased disproportionately.

This chapter focuses firstly on the expansion of internment and confinement between 1915 and the beginning of 1917 in Europe and outside it. It traces the differences among the various belligerents in the treatment of enemy aliens, the living conditions in the camps, and the national, gender and generational composition of the inmates. It also concentrates on the one hand on the popular pressure in support of the wholesale internment of enemy aliens and, on the other, on the broadening of the humanitarian activities pursued by international non-governmental organization such as the International Committee of the Red Cross that actively promoted the exchange of prisoners of war and civilian internees. The second part of the chapter addresses the spread of a nationalistic economic discourse that boosted the intensification of the economic war and the attack on enemy aliens' property with the creation of new state bureaucracies and the beginning of the liquidation of sequestered assets. The chapter shows how the capacity of the state to enforce such policies was continuously put to the test by the effect of the war on politics and by its military evolution.

This chapter follows the globalization and radicalization of the policies on enemy aliens that occurred in the last two years of the war. In 1917, the conflict became truly global with the entrance of the Americas (the United States, Brazil and Cuba) and Asia (the independent states of China and Siam, and the Philippines as a US dependency). At the same time, Russia and Romania exited the conflict, signing disadvantageous peace agreements with Germany. All the states that joined the war in 1917 drew up policies against enemy aliens, notwithstanding the enormous differences in the numbers of such people within their territories. The chapter analyzes the policies against enemy aliens in the United States, in Brazil, in China and Siam, and compares them with the evolution of the war in Europe where radicalization transformed all foreigners into enemies and also affected neutral countries. The chapter concentrates in particular on a series of new developments that concerned property rights. On the eve of the end of the conflict, property rights were no longer safe in any of the belligerent countries and were actually in pieces in many places.