Abstract The French Marxist economist Charles Bettelheim (1913–2006) conducted after the end of World War II important scientific activity on economic planning, together with an international consulting activity in developing countries, as a non-Soviet expert on Soviet planning. He was the Frenchman who whispered the Soviet way of planning in the ears of Nasser in Egypt, Nehru in India, and Che Guevara in Cuba, to mention only three obvious examples. The expression “planning doctors” is proposed in this article to designate this kind of economist who advised governments in the setting up of socialist five-year plans. In order to understand how Bettelheim became a planning doctor, the article reconstructs the formative period of his career and what role World War II played in this making, starting with his studies in political economy in France, his trip to the USSR in 1936, and his works on Soviet statistics. It is shown how World War II affected Bettelheim from an intellectual point of view, with his study of the German economy at war, and from an institutional point of view, as his encounters during the war proved instrumental for the setting of his postwar career as a planning doctor.