Hans Julius Zassenhaus (28 May 1912 – 21 November 1991) was a German mathematician, known for work in many parts of abstract algebra, and as a pioneer of computer algebra. Biography He was born in Koblenz in 1912. His father was a historian and advocate for Reverence for Life as expressed by Albert Schweitzer. Hans had two brothers, Guenther and Wilfred, and sister Hiltgunt, who wrote an autobiography in 1974. According to her, their father lost his position as school principal due to his philosophy. She wrote: Hans, my eldest brother, studied mathematics. My brothers Guenther and Wilfred were in medical school. ... only students who participated in Nazi activities would get scholarships. That left us out. Together we made an all-out effort. ... soon our house became a beehive. Day in and day out for the next four years a small army of children of all ages would arrive to be tutored. At the University of Hamburg Zassenhaus came under the influence of Emil Artin. As he wrote later: His introductory course in analysis that I attended at the age of 17 converted me from a theoretical physicist to a mathematician. When just 21, Zassenhaus was studying composition series in group theory. He proved his butterfly lemma that provides a refinement of two normal chains to isomorphic central chains. Inspired by Artin, Zassenhaus wrote a textbook Lehrbuch der Gruppentheorie that was later translated as Theory of Groups. His thesis was on doubly transitive permutation groups with Frobenius groups as stabilizers. These groups are now called Zassenhaus groups. They have had a deep impact on the classification of finite simple groups. He obtained his doctorate in June 1934, and took the teachers’ exam the next May. He became a scientific assistant at University of Rostock. In 1936 he became assistant to Artin back in Hamburg, but Artin departed for the USA the following year. Zassenhaus gave his Habilitation in 1938. According to his sister Hiltgunt, Hans was "called up as a research scientist at a weather station" for his part in the German war effort. Zassenhaus married Lieselotte Lohmann in 1942. The couple raised three children: Michael (born 1943), Angela (born 1947), and Peter (born 1949). In 1943 Zassenhaus became extraordinary professor. He became Managing Director of the Hamburg Mathematical Seminar. After the war, and as a fellow of the British Council, Zassenhaus visited the University of Glasgow in 1948.