In time, he became persuaded of the importance of offering his testimony, which he gave to thousands of students in the later years of his life. He drew a distinction between recollection, which he said dies with the person who carries it, and memory, which he compared to a thread linking the past and future.

One student was so moved by his story that he or she left him an anonymous note asking for forgiveness for the actions of a fascist grandfather.

“I would like to respond with these words,” Mr. Terracina said in public remarks reported by the Italian news agency ANSA. “Don’t worry, young man or young woman. Your grandfather’s actions are a lesson for you, but grandchildren do not bear the guilt for what their grandparents have done, just as children do not bear the guilt for what their parents have done. What matters is that you recognize and understand the lesson, what is right and what is wrong.”

By 1940 Nazi Germany had assigned the Gestapo to turn Terezín into a Jewish ghetto and concentration camp.  It held primarily Jews from Czechoslovakia, as well as tens of thousands of Jews deported chiefly from Germany and Austria, as well as hundreds from the Netherlands and Denmark. More than 150,000 Jews were sent there, including 15,000 children, and held there for months or years, before being sent by rail transports to their deaths at Treblinka and Auschwitz extermination camps in occupied Poland, as well as to smaller camps elsewhere.  Less than 150 children survived.

Although Terezin was not an extermination camp, about 33,000 died in the ghetto. This was mostly due to the appalling conditions arising out of extreme population density, malnutrition and disease. About 88,000 inhabitants were deported to Auschwitz and other extermination camps.  At the end of World War II, there were 17,247 survivors of Terezin (including some who had survived the death camps).

Many educated Jews were inmates of Terezin. Unlike other camps, Terezin’s detainees included scholars, philosophers, scientists, visual artists, and musicians of all types, some of whom had achieved international renown, and many of these contributed to the camp's cultural life. The Nazis kept a tight rein on the world’s perception of activities within Terezin.  In a propaganda effort designed to fool the Western allies, the Nazis publicized the camp for its rich cultural life.  
The Czech composer Rafael Schächter was among those held at the Terezin camp.  In 1943, he conducted an adult chorus of 150 Jews which engaged in 16 performances of the massive and complex Requiem by Giuseppe Verdi before audiences of other prisoners, SS officers, and German army staff members.

In late 1943 an inspection of Terezin was demanded by Christian X, king of Denmark, to determine the condition of 466 Danish Jews sent there in October of that year. The review panel was to include two Swiss delegates from the International Red Cross and two representatives of the government of Denmark.  The Nazis permitted these representatives to visit Terezin in order to dispel rumors about the extermination camps.
The Germans immediately engaged in an infamous beautification program – “Operation Embellishment,” a ruse intended to mollify the king’s concerns.  Weeks of preparation preceded the visit. The area was cleaned up, and the Nazis deported many Jews to Auschwitz to minimize the appearance of overcrowding in Terezin. Also deported in these actions were most of the Czechoslovak workers assigned to "Operation Embellishment". The Nazis directed the building of fake shops and cafés to imply that the Jews lived in relative comfort.  
The inspection was held on June 23, 1944.

The Danish Jews that the Red Cross visited, lived in freshly painted rooms, not more than three in a room. The Red Cross representatives were conducted on a tour following a predetermined path. The representatives apparently did not attempt to divert from the tour route on which they were led by the Germans, who posed questions to the Jewish residents along the way. If the representatives asked residents questions directly, they were ignored, in accordance with the Germans' instructions to the residents prior to the tour.  Despite this, the Red Cross apparently formed a positive impression of the town.
As part of the charade the Nazis compelled Schächter to give a performance of the Requiem. According to the United States Holocaust Memorial Museum, the Red Cross issued “a bland report about the visit, indicating that the representatives were taken in by the elaborate fiction.”  Eichmann was later quoted as having said, “Those crazy Jews—singing their own requiem.”  Rafael Schächter was deported to Auschwitz on October 16, 1944, and died the following day in the gas chamber.

 Following the successful use of Terezin as a supposed model internment camp during the Red Cross visit, the Nazis decided to make a propaganda film there. It was directed by Jewish prisoner Kurt Gerron, an experienced director and actor. Shooting took eleven days, starting September 1, 1944.  After the film was completed, most of the cast and the director were deported to Auschwitz. Gerron was murdered by gas chamber on October 28, 1944.

The film was intended to show how well the Jews were living under the  benevolent protection of the Third Reich. Often called “The Führer Gives a Village to the Jews,” the correct name of the film is “Theresienstadt. Ein Dokumentarfilm aus dem jüdischen Siedlungsgebiet “("Terezin: A Documentary Film of the Jewish Resettlement").  As the film was not completed until near the end of the war, it was never distributed as intended, although a few screenings were held. Most of the film was destroyed, but some footage has survived.