 Jules Henri Poincaré was born on April 29, 1854 in Nancy in the Lorraine region of France. His father was professor of Hygiene in the School of Medicine at the University of Nancy. His cousin Raymond was to become the President of the Republic of France during the period 1913–1920 and his younger sister Aline married the philosopher Emile Boutroux. Henri was a precocious student who rose immediately to the top of his class, excelling in both science and letters. At age 13, his teacher told his mother that “Henri will become a mathematician … I would say a great mathematician” (Bellivier 1956: 78). During the Franco-Prussian war in 1870 the Germans occupied Nancy and the Poincaré family was obliged to billet the secretary of the civil commissar of Nancy, with whom Henri would have a round of conversation each night after dinner in order to improve his German (see Rollet 2012).