Leonard Polak was professor in philosophy at the University of Groningen. On his suspension from that post, he sent a protest letter to his university colleagues. In the letter, he called the Nazis 'the enemy'. The Rector Magnificus forwarded the letter to the German authorities.
After his suspension as professor, he continued to lecture at the People's University in Groningen. On 15 February 1941, Leonard Polak was arrested. Via prisons in Groningen and Leeuwarden, he was deported to Sachsenhausen concentration camp where he was killed in the Kommando Oranienburg on 9 December 1941.
NIOD, Erelijst Verzet en Koopvaardij, database made by J.W. de Leeuw, and: J. Presser, Ondergang. De vervolging en verdelging van het Nederlandse jodendom 1940-1945. Deel I (Den Haag 1965) 96-97
Leonard Polak is remembered in the book Prof. Mr. Dr. Leo Polak : een erflater van onze beschaving : herdacht door vrienden en collegæ gevolgd door de voordracht de zin van de dood (Amsterdam 1946)
There is a headword for Leonard Polak in the Biografisch Woordenboek van Nederland.
This person is commemorated on a memorial in Groningen. More information on this memorial can be found (in Dutch) on the website of the Nationaal Comité 4 en 5 mei.
Leonard Polak is also commemorated on Jewish Monument Zaanstreek