This chapter inquires how the historical context and biographical formative experiences shaped Lemkin’s intellectual career, leading to the definition of crimes of barbarity and vandalism, and later inventing the term ‘genocide’. It critically contextualizes Lemkin’s role at the dawn of international criminal law, showing the importance of his warnings and actions against the Holocaust, but also his romantic belief in the power of international law, his idealism, inconsistencies and contradictions. On one hand, Lemkin raised a strong voice of advocacy for individual rights when criticizing the Soviet and the Italian penal codes in the 1920s; on the other, he became obsessed almost atavistically with the collective rights and the criminal intent to destroy ethnic, religious and national groups. In his emphasis on groups he departed from humanitarian law and human rights, both focusing on the individual. Lemkin’s life, private and public, was uneven; he simply could not find purpose in anything else than the Genocide Convention and its ratification.