The Opinio Juris and Opinio Moris in the Anglo-American Interventions During the Greek Civil War: An Archival Study of Legal Narratives

Abstract This article investigates the British and American interventions in Greece during the Greek Civil War, examining their legal and moral justifications. Using archival documents, the study uncovers two primary layers of discourse: the official diplomatic language of opinio juris (conviction of legality) and opinio moris (conviction of morality), alongside the covert political interests that drove these interventions. The research argues that British and American actions were primarily motivated by a ‘conviction of interest,’ with legal and moral narratives used tactically to justify their interventions. The archival materials reveal a notable lack of empathy and understanding from British and American officials regarding the trauma endured by the Greek populace due to the German occupation and collaborationist violence. Additionally, there was a significant neglect of the will of the Greek people. The study critically examines the Caserta and Civil Affairs Agreements, which provided a legal basis for British intervention, arguing that these agreements, when viewed in light of the Vienna Convention on the Law of Treaties, fail to justify the extent of foreign interference, thus questioning the authenticity of Greek consent. The article also explores the transition from British to American dominance in Greek affairs. As Britain faced economic constraints after the end of WWII, it ceded its role to the U.S., leading to the formulation of the Truman Doctrine and the implementation of the Marshall Plan. The U.S. intervention is analyzed through legal and geopolitical lenses, revealing a strategic focus on preventing communist expansion rather than providing purely legal or moral support for Greece’s recovery. Similar to British actions, American involvement often overlooked the political situation and the will of the Greek people, thereby contributing to prolonged instability.