At six years of age he was deported to Nazi concentration camps in Austria (Strasshof and Floridsdorf), together with his mother and siblings.
[5] Greenblatt studied at Yeshiva Chaim Berlin, then attended Brooklyn College, then Yale, where he received his PhD in mathematics in 1963, at the age of 25, under American mathematician William Schumacher Massey.
[9] In 1966, Greenblatt became very involved in the anti war movement and organized a series of teach-ins in order to "educate Americans about the tragic errors of our Vietnam policies.
He was one of the chief organizers of the Spring Mobilization to End the War in Vietnam, scheduled for both New York City and San Francisco on April 15, 1967.
[10] In 1969 Greenblatt was subpoenaed by The House Un-American Activities Committee, who seized a large quantity of documents and forced him to testify.
[14] Greenblatt's cross examination was led by Richard Howard Ichord Jr., last chairman of the House Un-American Activities Committee.
Greenblatt was quite combative with the committee, arguing that their actions were reminiscent of the fascist tendencies he had escaped from in Nazi occupied Europe.
I spent years in concentration camps in Germany under the most blatant kind of Fascist rule — which again, and at that time, was justified, in the name of protecting the security of the countries then involved.
I am very concerned about the kind of actions that the committee and law enforcement officers, or people who should be enforcing the law, have taken against myself, attorneys, other witnesses, colleagues of mine that have appeared or tried to appear before this committee…….. And I must say at this time, specifically, that the greatest outrage was reached in the last few days when, in fact, one of my colleagues, one of my brothers, was physically assaulted outside this committee.
[citation needed] One of his children, Brooklyn artist Jeremiah Grunblatt, died in a car crash on his honeymoon in October 2015, three days after his wedding.