De Gaulle returned to France, where he became a lecturer in military history at St Cyr. He was already a powerful speaker, after practice as a prisoner of war. He then studied at the "École de Guerre" (staff college) from November 1922 to October 1924. Here he clashed with his instructor Colonel Moyrand by arguing for tactics based on circumstances rather than doctrine, and after an exercise in which he had played the role of commander, he refused to answer a question about supplies, replying ""de minimis non-curat praetor"" ("a leader does not concern himself with trivia") before ordering the responsible officer to answer Moyrand. He obtained respectable, but not outstanding grades – 15 or so out of 20 – on many of his assessments. Moyrand wrote in his final report that he was "an intelligent, cultured and serious-minded officer; has brilliance and talent" but criticised him for not deriving as much benefit from the course as he should have done, and for his arrogance: his "excessive self-confidence", his harsh dismissal of the views of others "and his attitude of a King in exile". Having entered 33rd out of 129, he graduated in 52nd place, with a grade of "assez bien" ("good enough"). He was posted to Mainz to help supervise supplies of food and equipment for the French Army of Occupation.