This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
From 1941 to 1946, French colonial authorities arrested Cao Dai's leader Pham Cong Tac and held him, along with other Caodaist figures, in penal colonies in Madagascar, removing the movement's own leadership from Vietnam for the whole of the Second World War. Pham Cong Tac had succeeded the religion's founding leader, Le Van Trung, in 1934, so the exile struck the movement at its very top rather than at some peripheral figure the faith could easily replace.
The colonial authorities who carried out the arrests acted against a movement they read as a political threat as much as a religious one, sweeping up Caodaist leadership figures broadly rather than targeting Pham Cong Tac alone. Held far from Vietnam in Madagascar for five years, the exiled leadership could not direct the movement's affairs at home during exactly the years the Second World War was reshaping the whole of Indochina around them.
What the exile changed for Cao Dai's spread was continuity itself: a movement barely fifteen years old, still built around the authority its early leaders carried personally, had to survive the entire span of a world war with its own recognized leader held on another continent, and its eventual recovery after 1946 depended on that leadership, and the movement built around it, still being there to return to.