Ben was born in a small village in the Carpathian Mountains of Transylvania in Romania. When he was an infant, his family moved to the United States. Ben attended Harvard University, where he studied criminal law. Ben graduated from Harvard University Law School in 1943. He joined a US anti-aircraft artillery battalion that was training in preparation for an Allied invasion of western Europe. At the end of World War II in Europe, Ben was transferred to the war crimes investigation branch of the US Army. He was charged with gathering evidence against and apprehending alleged Nazi war criminals. He ultimately became chief US prosecutor in The Einsatzgruppen Case of the Subsequent Nuremberg Proceedings.
I recall having nailed up the sign: Headquarters, Third United States Army, War Crimes Trials, Dachau. Uh, we decided that we were going to have the trials in Dachau. Now Dachau was liberated by the Seventh Army, not the Third Army, but we were occupying, General Patton was there, and that was the site, that's where we were going to have trials. And so we took these army officers who had been assigned to the Judge Advocate section, not because they were lawyers but because they were at liberty and we needed staff and they had nobody else. And, uh, they were going to set up tribunals. These were in fact military tribunals, uh, they are not to be confused with, uh, what happened later at the International Military Tribunal at Nuremberg, which was an international court. These were military-style tribunals which have existed under the laws of war for a very long time. And, uh, they were staffed by, uh, military officers, similar to a court martial, it followed the court martial procedure. So that you would have three officers, a colonel, a major, a captain, a whatever, the highest ranking was the presiding officer, the prosecutors were selected by the Judge Advocate group, they may or may not have been lawyers, sometimes they were, sometimes they weren't. They were a lieutenant assigned to defend so-and-so or, uh, to prosecute so-and-so, as they would a soldier who'd gone AWOL. And, uh, then they had all these nice reports, prepared by me, by Nowitz [ph], by a few other guys, Slotnik [ph] was another lawyer who came on board, and we had a fellow name of Briggs [ph] who was a lawyer, went up to Boston, all these were enlisted men, and, uh, they did all the work. And they'd have these reports, and based on those reports they would, we would draw up the indictment, I would draw up the indictment. Uh, and the indictment would say that, uh, SS Major so-and-so is indicted for mass murder of so many concentration camp inmates of such-and-such camp during such-and-such period when he was in command. And the evidence is: photographs obtained by the Signal Corps, statements from the survivors, my own affidavit or other affidavits of, for witnesses who were there, usually not my own, I would certify to the procedures whereby these affidavits were obtained. And, uh, on the basis of that the defendant would be asked, "How do you plead?" And they'd say, "I plead not guilty." "All right, let's proceed with the trial."