Number theory plays a specific role in the current image of French mathematics during the interwar period: it is seen as being totally absent until the 1930s, when the future founders of Bourbaki import it from Germany; it is thus deeply linked with this group’s renewal of French mathematics. This text reexamines this issue with new sources, in particular mathematical articles and talks in the domain during the period. These sources shed light on the traces of a Hermitian tradition in number theory, centered on forms and linked to analysis; quite different from the algebraic number theory promoted by the heirs of Richard Dedekind and David Hilbert. The role of the First World War in the quasi-disappearance of this trend is then studied through individual trajectories: this study shows that strictly mathematical priorities are not the only ones at stake, and convictions concerning what constitutes a mathematical life also play a decisive role in this process.