During the interwar period, the International Labor Office endeavored to regulate world migrations. It urged governments to sign conventions in order to develop international law and guarantee social rights to migrant workers, including social insurance covering retirement, disability, health, unemployment, and work injuries. Led by an international network of social reformers such as Albert Thomas and Arthur Fontaine, the ILO claimed that the diffusion of the Welfare State was a prerequisite for fair economic competition. Supported by non-governmental organizations defending migrants’ rights (often in association with churches), bringing together top-ranking civil servants, employers, and trade-unionists, the ILO claimed supranational authority to compel nations to more equally share raw materials and manpower. However, the have-nots (powerful countries without colonial empires), who relied on demographic concepts such as optimum or overpopulation, hijacked this breach of the principle of national sovereignty. For the sake of the supreme interests of mankind, the ILO’s social reformers unwittingly paved the way for a doctrine that would later be used to justify the territorial aggressions of the 1930s like those in Manchuria and Ethiopia.