A French Defence Ministry directorate. It has three principal missions: to equip the French armed forces by developing, buying, evaluating and testing military equipment in partnership with industry; to prepare the future by ensuring technologies and know-how remain up-to-date; and to promote French defence industry exports.
For those of you unfamiliar with the French education system, the École Polytechnique is the most prestigious engineering school in the country, a sort of MIT/Stanford rolled into one, with the specificity that it is a military school so the students are paid as young officers, wear a uniform and are expected to work for the state for at least 10 years after graduation. Following the three-year course, all students go onto further studies to a "school of application" i.e. a professional higher education engineering school to specialise in aerospace, telecoms, electricity etc.