The International Bureau of Education (IBE) was founded in 1925 to promote peace through science and education, and to federate other international agencies working towards similar goals. In 1929 it became a pioneering intergovernmental organisation in education, actively collaborating with the UNESCO since 1948. Despite exacerbated nationalisms throughout the 1930s, the number of countries that joined the IBE’s council steadily grew. Notwithstanding border closures enforced during the Second World War, the IBE remained active, particularly via the Service of intellectual assistance to prisoners of war (SIAP). Within this crisis context of a particularly restrictive nature, how did the IBE sustain its educational mission and its internationalist posture ? This chapter describes the SIAP’s « birth », implementation, and operation, then proceeds to problematise the challenges to which the Bureau is confronted. We make the case that the project’s implementation is not without tension, as it faces off with certain limits of intergovernmental practices, resulting in differentiated treatment depending on beneficiaries’ nationalities.