 An academically gifted boy, Cogny was awarded a scholarship to École Polytechnique, where he received an engineering degree, a diploma from the French Institute of Political Science, and a doctorate in law.Cogny enlisted in the French Army before the outbreak of World War II, graduating in 1929 from the Fontainebleau artillery school, and was a battery commander by the time the war started.He was awarded the Croix de guerre during early engagements.