Struik commuted from Rotterdam to Leiden University by train, so he never became fully involved with student life. He described his undergraduate years in :-
No one ever told you which lectures to hear if you wanted to pass your exams; the grapevine took care of that, and you just followed the others who were in the same boat. No deans, provosts, marshals, student advisors, psychologists, and other such academic sages. No fortnightly tests either; there were just two exams in four years ...The range of courses studied by Struik included mathematics and physics. In physics he was taught by Lorentz and de Sitter. Lorentz retired in 1912 when Ehrenfest was appointed to his chair. Struik was strongly influenced by Ehrenfest and attended the weekly seminar which he set up. In 1917, while working on a dissertation, his funds ran out and he left the university to take up a post teaching mathematics in a school in Alkmaar, north of Amsterdam.
However, he received a letter from J A Schouten asking if he would like to become his assistant. Ehrenfest had recommended Struik and, after worrying about leaving a teaching post he enjoyed, he decided to accept Schouten's offer and joined him in Delft. Struik decided to change to the topic he was studying with Schouten, tensor analysis, for his doctoral thesis and he presented his dissertation on applications of tensor methods to Riemannian manifolds in 1922.
Struik was appointed to a post at the University of Utrecht in 1923. The same year he married a Czech mathematician Ruth Ramler who had obtained a doctorate in mathematics from the University of Prague under the supervision of G Pick and G Kowalewski. However Struik was by this time known for left wing views and this made his academic future look uncertain. In September 1924, funded by a Rockefeller Fellowship, the Struiks spent nine months in Rome. There Dirk worked with Levi-Civita and Ruth worked with Enriques. They had the chance to meet many other mathematicians, Amaldi, Castelnuovo, Volterra and Bianchi who were working in Rome as well as Hadamard, Zariski and Aleksandrov who were visiting Rome.
It was while Struik was in Rome that he first became interested in the history of mathematics. However this interest was about to take a new turn, for in June 1925, with an extension of his Rockefeller Fellowship he arrived in Göttingen. Klein, a great mathematical hero of Struik's, died only days after Struik arrived in Göttingen to work with Courant. Courant approached Struik to prepare an edition of Klein's lectures on the history of 19th century mathematics for publication. Another important event at Göttingen for Struik was meeting Norbert Wiener there.
While at Göttingen, Struik made full use of the excellent library there to study the Renaissance mathematicians Ries, Rudolff, Apianus, Stifel and Stevin. When his Fellowship ended he returned to Delft but with no prospect of a permanent post. When he received offers from Otto Schmidt to go to Moscow and from Norbert Wiener to visit MIT he had to choose one but it was a hard choice. He decided to visit the USA and left for New York in November 1926.
Struik was to work at MIT for the rest of his career. It was a career based on collaboration with Wiener, a continued collaboration with Schouten and an increasing involvement with the history of mathematics. The years of World War II brought changes as Alberts notes in :-
During the war years much of the normal mathematical research activity at MIT came to a standstill. Some of the professors were involved in research for the military; others, including Struik, carried heavy teaching duties connected with the training of military personnel. Aside from this, Struik spent much of his time pursuing an entirely new research project: to study the origins of American science in their social and economic setting, a subject that had barely been touched on by historians before this time. Even more significantly, the dialectical-materialist approach Struik adopted towards this subject was unprecedented.Struik's Marxist views, however, were bound to lead to trouble in the McCarthy era and indeed this is exactly what happened.
At first the McCarthy period was, as Struik put it:-
... half reminiscent of Nazi Germany, half of Alice in Wonderland.In April 1949 he was accused by an F.B.I. informant. By July 1951 he was charged with being a member of the Communist Party and having taught Marxism. He was brought before the House Un-American Activities Committee and, on legal advice, invoked the Fifth Amendment and refused to answer each of over 200 questions that were put to him.
Struik was later indicted on charges and bail set at $1000 which was put up by friends who supported him. He was suspended from MIT, with salary, while he was indicted. Since there was no real evidence against Struik the case was not brought, but on the other hand it was not dropped until 1955. During this period Struik concentrated on historical projects, having been prevented from teaching.
By late 1955 Struik was reinstated in his teaching duties and held these until 1960 when, at the age of 65, he had to retire. MIT refused him an Emeritus position and his attempts to find positions in other universities in the United States failed. He eventually accepted invitations from Puerto Rico, Costa Rica and Utrecht. He turned his attention to a number of topics of special interest to him, in particular to promoting the history of the sciences, especially mathematics, in Latin America.
In  a former student at MIT described Struik's teaching:-
He taught mathematics not as some esoteric mystery, but as practical common sense. And yet, at the same time he gave us a glimpse of the sheer beauty of it. It was at this time that I understood Edna St Vincent Millay's line "Euclid alone has looked on beauty bare".
Article by: J J O'Connor and E F Robertson