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An industrial accident in 1907 cost Lefschetz both hands; he switched from engineering to mathematics and went on to reshape algebraic topology, producing the Lefschetz fixed-point theorem and the Lefschetz hyperplane theorem, tools that became standard equipment for studying algebraic varieties. Born in Moscow, he spent most of his career at Princeton and later built Brown University's center for nonlinear differential equations into the field's largest research group. He won the National Medal of Science in 1964, decades after a disability that would have ended most careers instead redirected his.