Guillaume Apollinaire is without doubt the most prolific French poet of the Great War. In addition to his major poetry collection, Calligrammes (1918), he wrote and published plays, stories, journalism, and criticism during the conflict. His writing is nothing if not wide ranging.He considered poetry a spiritual activity and an escape from the traditional classification of genre. He also believed there was no boundary between art and life – the two are inextricably linked – and, further, that art and life transform one another.This porous nature, not without its ambivalences and paradoxes, constitutes a major key to the interpretation of his work. The diversity and originality of his oeuvre, the trajectory of the author and the importance of his legacy help to explain how and why he became a poet of war in France, a country that ignored the tradition of 'war poets' that had developed in Great Britain.