David Cohen was born on 31st December 1882 in Deventer as the oldest son of salesman, estate agent and surveyor Hartog (Herman) Cohen and Rebecca van Essen. Later, three brothers and one sister would join the family. He attended primary school, Jewish school and high school in his place of birth and then studied classical languages in Leipzig, GŲttingen and Leiden. His greatest interests lay in egyptology, papyrology and Jewish history. After 1910, he combined his studies with a teaching job at the Nederlands Lyceum in The Hague. In 1912, he earned his doctorate degree in Leiden cum laude, which he wrote about Jewish history during the Hellenistic period. In 1922, he became a privatdozent at the University of Leiden and two years later he became a visiting professor of the history of the Hellenistic period. In 1926, he became the Professor of Ancient History and the Greek and Roman Antiquities at the University of Amsterdam, a position he held until 1953.
Cohen was a professor who knew the ins and outs of his field but was more of a lecturer than a researcher. He did little in the way of original research; his passion was for teaching. He wrote several important textbooks about ancient history and mentored many doctoral students. In Cohenís mind, the classical antiquity was the ideal world, where goodness and beauty dominated. He used examples from this world to show how the modern world could be improved. He was certainly not locked away in an ivory tower, as he is unduly described by some, but someone who was grounded in reality and full of compassion for repressed groups in society.
Cohen was active in all sorts of Jewish organisations during his life. At the age of 20, he established an organisation in Deventer that was affiliated with the Dutch Zionist Federation, an organisation that was set up in 1899 with the goal of collecting funds to allow Eastern European Jewish refugees so they could be trained in agriculture and start a new life in Palestine or the USA. Between 1905 and 1909 he was an editor of De Joodsche Wachter (The Jewish Guardian), part of the Dutch Zionist Federation. He was also a member of the Permanent Committee of the Dutch Israelite Church Association, a governing member of the Association for Jewish Science and the curator of the Dutch Israelite Seminar. In the period between 1933 and 1940 he was extremely active in helping Jews refugees who had fled Nazi Germany. From 1933 onwards, Cohen spent a great deal of his time on this humanitarian work, during which he developed important international connections. He was the founder and secretary of the Committee for Special Jewish Interests, an organisation with many branches such as the most important, the Committee for Jewish Refugees, of which he was the chairman. In both positions, he worked intensively with Abraham Asscher, with whom he was a co-chairman of the Jewish Council during the years between 1941 and 1943.
Cohen grew into a competent leader. His success was due to the combination of deep self-discipline, an enormous sense of duty, stoicism and composure. He rapidly gained a leadership role within the Dutch Jewish community. When the Germans invaded the Netherlands in 1940, he immediately started a Jewish organisation to ward off the dangers of the expected race politics of the occupier. In December 1940, the Jewish Coordination Committee commenced under the chairmanship of Mr. L.E. Visser, the ex-president of the Hoge Raad, who was fired by the Germans. Cohen became a member and not a secretary, the resistance against his often authoritarian behaviour had grown too great for him to be allowed that role. The Jewish Coordination Committee was not destined to last long because of their refusal to negotiate with the German occupiers and their resolve to only work with representatives of the Dutch government. This was an attitude that mostly belonged to Mr. Visser. Cohen and Asscher advocated a significantly more flexible attitude towards the occupiers. In a written exchange with Visser, Cohen contrasted Visser's idealism and integrity with his own pragmatism and sense of reality.