page_title: Jean-Victor Poncelet
section_title: Birth, education, and capture (1788–1814)
hierarchical_section_title: Jean-Victor Poncelet / Biography / Birth, education, and capture (1788–1814)
caption_attribution_description: Cloître sainte Constance (lycée Fabert de Metz) vu depuis l'opéra théâtre
context_page_description: Jean-Victor Poncelet was a French engineer and mathematician who served most notably as the Commanding General of the École Polytechnique. He is considered a reviver of projective geometry, and his work Traité des propriétés projectives des figures is considered the first definitive text on the subject since Gérard Desargues' work on it in the 17th century. He later wrote an introduction to it: Applications d'analyse et de géométrie.
  As a mathematician, his most notable work was in projective geometry, although an early collaboration with Charles Julien Brianchon provided a significant contribution to Feuerbach's theorem. He also made discoveries about projective harmonic conjugates; relating these to the poles and polar lines associated with conic sections. He developed the concept of parallel lines meeting at a point at infinity and defined the circular points at infinity that are on every circle of the plane. These discoveries led to the principle of duality, and the principle of continuity and also aided in the development of complex numbers.
context_section_description: Poncelet was born in Metz, France, on 1 July 1788, the illegitimate then legitimated  son of Claude Poncelet, a lawyer of the Parliament of Metz and wealthy landowner. At a young age, he was sent to live with the Olier family at Saint-Avold. He returned to Metz for his secondary education, at Lycée Fabert. "Lycée" is the French name for high school. After this, he attended the École Polytechnique, a prestigious school in Paris, from 1808 to 1810, though he fell behind in his studies in his third year due to poor health. After graduation, he joined the Corps of Military Engineers. He attended the École d'application in his hometown during this time, and achieved the rank of lieutenant in the French Army the same year he graduated.
  Poncelet took part in Napoleon's invasion of Russia in 1812. His biographer Didion writes that he was part of the group which was cut from Marshal Michel Ney's army at the Battle of Krasnoi and was forced to capitulate to the Russians, though other sources say that he was left for dead. Upon capture, he was interrogated by General Mikhail Andreyevich Miloradovich, but he did not disclose any information. The Russians held him as a prisoner of war and confined him at Saratov. During his imprisonment, in the years 1812–1814, he wrote his most notable work, Traité des propriétés projectives des figures, which outlined the foundations of projective geometry, as well as some new results. Poncelet, however, could not publish it until after his release in 1814.
caption: The Lycée Fabert in Metz, where Poncelet was fellow student.
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