The internationalization of education (IE) has accelerated across the past two decades. Although there are now a range of representations and theorizations of IE, they find little connection across domains and levels. Toward bolstering a more coherent field of IE, which translates across distinctive expressions of IE, this paper argues for a conceptual approach that includes theorizing IE's past and present enabling conditions, motivating visions, significant (operational) obstacles, and ensuing tensions. The main contribution is a conceptualization of late 20th century international education, which historically situates the current 21st century IE movement. This conceptualization is informed primarily by a periodization of the International Baccalaureate that surfaces the semantic contours and structuring tensions of international education as embedded in the shifting historical and socio-political conditions of the last 50 years. Semantically, 20th century international education carries with it literal (educational activities across national jurisdictions) and normative/aspirational significations (liberal-humanist education for making a better world). And the structuring tensions of international education are constituted in the entangling of the normative visions, as "education for international understanding," with the instrumental agendas, as revenue generation. An emerging IE field can draw on the conceptual framing offered in this paper as a basis for theorizing across the somewhat siloed IE discourses.