It is considered to be the first act of resistance of World War II in France, one day before Charles de Gaulle's Appeal of 18 June.

He helped many victims of the Nazis in occupied France, including Catholic philosopher Dietrich von Hildebrand.

In 1943 he was arrested and incarcerated at the Dachau concentration camp where he assisted other prisoners during a typhus epidemic and was infected himself.

In 1963 he founded the France-Algeria Association to encourage cooperation between France and the newly independent Algeria.

Michelet was the main collaborator of Abraham Vereide, the leader of the Family fundamentalist organisation, based in the United States.