"Alma Negra" (Black Soul): The Campaign for Free Labor in Angola and São Tomé, 1909-1916
Portuguese Studies Review
In the first two decades of the twentieth century, as European nations consolidated their empires across much of the world, humanitarians began to debate what separated free labor from coercion. There was little agreement beyond the idea that slavery, narrowly defined to mean the legal right to own another person, was unacceptable. Practices of forced labor by two colonizing powers in Africa -- King Leopold II's Congo Free State and Portuguese Angola and São Tomé in the Gulf of Guinea -- prompted international campaigns from free labor advocates for international regulation. Despite widespread concern over labor issues, however, there existed little agreement about what constituted unjustified force, especially in the colonial context where a non-European individuals's rights were rarely, if ever, recognized. Even the International Labor Organization (ILO), which was founded under the Paris Peace Treaties of 1919 and regarded the struggle against forced labor as one of its topmost priorities, conceded to the insistence of the European powers to not apply universal labor standards to colonies.
Ball , Jeremy. "'Alma Negra" (Black Soul): The Campaign for Free Labor in Angola and São Tomé, 1909-1916." Portuguese Studies Review 18, no. 2 (2011): 51-72. http://www.trentu.ca/admin/publications/psr/18_2.html