Jean-Victor Poncelet (1 July 1788 – 22 December 1867) was a French engineer and mathematician who served most notably as the Commanding General of the École Polytechnique.
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.As a military engineer, he served in Napoleon's campaign against the Russian Empire in 1812, in which he was captured and held prisoner until 1814.