Stefan Mazurkiewicz (25 September 1888 â 19 June 1945) was a Polish mathematician who worked in mathematical analysis, topology, and probability. He was a student of Wacà Âaw Sierpià Âski and a member of the Polish Academy of Learning (PAU). His students included Karol Borsuk, Bronisà Âaw Knaster, Kazimierz Kuratowski, Stanisà Âaw Saks, and Antoni Zygmund. For a time Mazurkiewicz was a professor at the University of Paris; however, he spent most of his career as a professor at the University of Warsaw.
In 1916, Mazurkiewicz introduced the concept of an opaque set: a collection of curves or segments that intersects all lines passing through a given region.
The Hahn-Mazurkiewicz theorem, a basic result on curves prompted by the phenomenon of space-filling curves, is named for Mazurkiewicz and Hans Hahn. His 1935 paper Sur l'existence des continus indécomposables is generally considered the most elegant piece of work in point-set topology.
During the PolishâÂÂSoviet War (1919âÂÂ21), Mazurkiewicz as early as 1919 broke the most common Russian cipher for the Polish General Staff's cryptological agency. Thanks to this, orders issued by Soviet commander Mikhail Tukhachevsky's staff were known to Polish Army leaders. This contributed substantially, perhaps decisively, to Polish victory at the critical Battle of Warsaw and possibly to Poland's survival as an independent country.