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.
Cogny enlisted in the French Army before World War II began, graduating from the Fontainebleau artillery school in 1929 and advancing to command a battery by war's start. He was decorated with the Croix de Guerre for his early combat efforts.