Stefan Banach (March 30, 1892 - August 31, 1945), a Polish mathematician, one of the moving spirits of the Lvov school of mathematics in pre-war Poland (see: Lviv). He was largely self-taught in mathematics; his genius was accidentally discovered by Hugo Steinhaus. When World War II began, Banach was President of the Polish Mathematical Society and a full professor of Lvov University. Being on good terms with Soviet mathematicians, he was allowed to hold his chair during the Soviet occupation of Lvov. The German occupation of the city in 1941 resulted in the mass murder of Polish academics. Banach survived, but the only way he could work for a living was by feeding lice with his blood in prof. Rudolf Weigl Institute where typhoid fever research was conducted. His health undercut during the occupation (lung cancer), Banach died before he could be repatriated from Lvov, which was incorporated into the Soviet Union, to Poland after the war.
Théorie des opérations linéaires (Teoria operacji liniowych, 1932) is regarded as Banach's most influential work. He also initiated and edited the Studia Mathematica series.
Stanislaw Marcin Ulam, another mathematician of the Lvov school of mathematics, in his autobiography, attributes this to Banach: "Good mathematicians see analogies. Great mathematicians see analogies between analogies".
Banach was the founder of functional analysis; he also made important contributions to the theory of vector spaces, measure theory, set theory and other branches of mathematics.