**Wilhelm Blaschke** was an Austrian mathematician whose research was on various aspects of geometry. He also initiated the study of topological differential geometry.

- There is another way that Josef Blaschke influenced his son, which was significant given the problems that he would later face, and this was to give him an international outlook making him very open minded in his approach to those from different countries.
- Wilhelm was brought up in Graz and it was there that he attended secondary school, graduating at the age of eighteen.
- Blaschke became extraordinary professor of mathematics at the Deutsche Technische Hochschule in Prague in 1913, remaining there for two years before moving to Leipzig in 1915.
- While in Leipzig, Blaschke published "Kreis und Kugel" Ⓣ(Circle and sphere) (1916) in which he investigated isoperimetric properties of convex figures.
- Although Weierstrass had supplied the missing proofs using the calculus of variations, this did not satisfy Blaschke who gave proofs in the style of Steiner in Kreis und Kugel Ⓣ(Circle and sphere).
- As with his previous position, Blaschke held the post at Leipzig for two years before moving on.
- Again Blaschke remained for about two years before moving to Tübingen.
- We do not mean to suggest that Blaschke stopped his travels when he took up the post in Hamburg.
- Blaschke was appointed to the Commission as a member of the Executive Committee of the German Mathematical Society.
- In June 1933 Blaschke organised a petition trying to persuade the government that forcing Reidemeister to retire at 40 years of age was detrimental to both the teaching of mathematics and mathematical research in Germany.
- Blaschke's petition was successful and Reidemeister was appointed to Hensel's chair at Marburg in what was considered a smaller and less prestigious university.
- The arguments were bitter and Blaschke won the day being himself elected Chairman of the German Mathematical Society in September 1934.
- However Bieberbach managed to prevent changes to the statutes of the Society that Blaschke attempted to introduce and the Reich Ministry of Education intervened forcing both Bieberbach and Blaschke to resign.
- Blaschke resigned the Chairmanship of the German Mathematical Society in January 1935 and at the same time also resigned from the Commission set up by the International Mathematical Union.
- Although up to this time Blaschke had strongly resisted certain Nazi policies, he seems to have had a change of heart in 1936.
- It was a process which Blaschke certainly supported, so when Germany invaded Austria on 12 March 1938 and Hitler annexed Austria on the following day, Blaschke approved.
- Blaschke was at this time in the rather difficult position of still being viewed with suspicion in Germany given his fight for internationalism.
- In 1939 Blaschke took part in a Congress in Rome from 22 to 28 October.
- Blaschke had made an attempt to prevent Bieberbach being named by the Reich minister as head of the German delegation, fearing that such an appointment would create trouble with both German and Italian mathematicians.
- However, Blaschke did not object to Bieberbach participating in the Congress.
- Although described as an international congress, only a few specially invited foreigners attended and Blaschke was one of a small number of Germans who were invited.
- On 28 July 1943 Blaschke went on holiday to the Tyrol with his wife.
- The rector indicates Blaschke's old sympathies with fascism.
- However, others such as Carathéodory argued that Blaschke should be reinstated so that relations among German mathematicians might improve.
- However the accusations against Blaschke were made more because his colleagues knew that he had Nazi sympathies rather than because he had done anything which caused harm to others.
- After Blaschke appealed against his dismissial he was reinstated on 23 October 1946 and continued to hold his chair in Hamburg until he retired on 30 September 1953.
- Blaschke's research was on various aspects of geometry.
- This volume was essentially a record of the contributions which Blaschke and his students had made to this topic, for it was a topic which eh had introduced and developed.
- In addition to an honorary degree which he received from Padua, which we mentioned above, Blaschke also received honorary degrees from Sofia University, Greifswald University and Karlsruhe Technische Hochschule.

Born 13 September 1885, Graz, Austria-Hungary (now Austria). Died 17 March 1962, Hamburg, Germany.

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Origin Austria

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive