The results of a recently published survey conducted in the United States by the Pew Research Center to mark International Holocaust Remembrance Day indicate that 45% of adult American citizens know that the Holocaust took the lives of six million Jews. Other responses to the question of how many Jews were murdered ranged from one million to three million. On one level, these responses lead to the obvious question of what can be done to rectify the widespread ignorance regarding the darkest days in human history. At the same time, they provide us with the opportunity to examine what precisely is the source for the well-known and terrifying iconic number of six million.Hundreds, if not thousands, of researchers are involved in the widely studied subject of the Holocaust. Indeed, the range of topics that are discussed in the academic literature is remarkable. The very fact that researchers continue to explore the subject today – seventy five years after the conclusion of World War II – is worthy of note. The thousands of studies, books, testimonies, films, exhibits, and memorial sites attest to the importance of the subject of the Holocaust and its study, and they provide a huge resource of material on which to base continued study in the twenty-first century. Every year, new materials and previously unknown information is revealed, testifying to the fact that even today, we only know a small amount about what occurred at that time. We will never know everything there is to know about the Holocaust. Elie Wiesel used to say that “the” book about the Holocaust has not yet been written, because it cannot be written; it is impossible to describe what actually took place.Yet the basic question remains: Where did the number six million come from?The difficulty in providing any number of victims of the Holocaust was articulated by Gideon Hausner, the Chief Prosecutor in the trial of Adolph Eichmann: One of the disagreements that we anticipate in the course of the trial relates to the number of victims of the Holocaust. The number six million has been sanctified in the public consciousness, but it is not so simple to prove that this number is accurate, and we therefore have not mentioned it in any official manner – but it is sacrosanct nonetheless.According to Yad Vashem, there is no data regarding the specific number of Jews killed during the Holocaust, but their researchers have concluded that “in every serious academic study, the number ranges between five and six million.” These researchers write that the number six million became widely accepted due to testimony at the trial of Adolph Eichmann, who served as the Minister of Jewish Affairs of the Reich’s Chief Security Office and filled a senior role in the implementation of the Final Solution. In August 1944, half a year before the conclusion of the war, Eichmann mentioned this number in conversation with one of his associates, Dr. Wilhelm Hutel, who testified to this effect at the Nuremberg trials.Other calculations in the research range from 5.1 million (Raul Hilberg) to 5.95 million (Yaakov Lashinsky) and 5.3-6.2 milllion (Lucy Davidowitz). A study conducted by Prof. Yisrael Guttman and Dr. Robert Rozet and published in the Encyclopedia of the Holocaust estimates the number of Jewish victims to be between 5.86-5.59 million, whereas a study conducted by Dr. Wolfgang Bentz approximates a total between 5.29-6 million. All of these numbers – including the one provided by Eichmann himself – were computed after the war’s conclusion. What was known about the extent of the devastation wrought by the Holocaust during the war itself – and who knew it?In an article titled “Yesh lispor ulesaper” (“We must count and recount”), published in April 1945, soon after the war’s end, well-known Jewish demographer and sociologist Dr. Yaakov Lashinsky wrote: “The five million victims demand an explanation, an answer, a clarification, a conclusion.” Did he not know at that point that the true number was much larger and even more terrible? When did this become apparent to the famous researcher, who went on to cite the number 5.95 million in his later research?Like all other Jews who grew up in Israel, I knew from the time of my youth that the destruction of the Holocaust took the lives of six million Jews. From the hundreds of books and studies on the topic that I have read and the thousands of documents that I have reviewed – including many from the Elie Wiesel Archive that have never been published – it is apparent that although the question of the total number of victims remains open in light of the ranges provided by German data and later research, the number six million remains imbedded in the popular psyche. I reached a deeper understanding of this topic due to my research on another topic. When I lived with my parents in Kibbutz Yavne, I became acquainted with a man who would visit my father, Rabbi Prof. Dov Rappel, at least once a year. The topic of their conversations always somehow related to the Holocaust. I once asked my father who the man was and why they spoke about the Holocaust whenever he visited. My father told me that the man was named Eliezer Ungar, one of the prominent leaders of the HaShomer HaDati religious Zionist movement in Poland, who had fled Poland in the midst of the war via Slovakia and Hungary, reaching Palestine after an extended period of flight. When Ungar left Hungry, he vowed “to rouse the entire world – all of humanity, and especially our brethren, the Jewish People.” To achieve this goal, he spread the word among the Jewish community in Palestine about the annihilation of the Jews in Europe. My father told me that already in 1944, right after he arrived in Palestine, Ungar would go from one synagogue to another, walk up to the central platform – with or without permission – and yell and scream on behalf of the Jews who still remained alive in Europe. He went to dozens of religious Zionist synagogues; most of the members did not want to hear him, and he was often thrown out. Although he found respectable work in Israel, he left the country in bitter despair in 1947 to serve in a number of capacities. Although he left the country physically, however, he never disengaged emotionally from the land and the country that he loved deeply. My father, who knew Ungar from the days of their joint activities in Ha-Shomer Ha-Dati in Poland, always provided him with a listening ear. Ungar would recount to him his exploits abroad and consult on matters of education, a subject close to his heart.In 2019, Bar-Ilan University held a joint conference of the Institute for Holocaust Studies and the Institute for Study of Religious Zionism. Given my connection to both institutes due to the nature of my work, I chose to present on a topic that relates to both – Eliezer Ungar. From the beginning of my research, it became apparent that there is very little written source material about him. I knew that Ungar had served for many years as an educational shaliach for the Zionist Federation, so I turned to the Zionist Archive and asked to see any paperwork related to him – but the massive archive only revealed one document. That lone document, however, proved to be very informative indeed.The document that I found was a protocol entitled “Statement of Eliezer Ungar at a Meeting of all of the Pioneer Organizations – January 19, 1944.” Just two days after he arrived in Palestine (on January 17, 1944), Ungar came to the meeting of the Zionist leadership in the country to present them with the harsh and painful reality. It was in the course of his presentation that he cited – for the first time, to the best of my knowledge – the number six million.Ungar began his words with the following statement: Polish Jewry is destroyed. It no longer exists. The Polish earth is the sanctified grave of Polish and European Jewry. I could have brought you a holy gift – a handful of dirt from the Polish soil, which has soaked up the blood of a nation that died the death of martyrs.Ungar continued his horrifying testimony: In the beginning of April 1943, we [in Poland] heard over the underground radio the cries of Rabbi Stephen Wise [an American Jewish leader] regarding two million Jews who had been murdered in Poland. We heard and we were astounded. Did the world not know that the number of the nation’s victims had already reached six million [emphasis in the original]?!Almost a year and a half before the war’s end, even before the mass destruction of Hungarian Jewry (400,000 Jews), one of the leaders of Ha-Shomer Ha-Dati in Poland testified that six million Jews had been murdered in Europe. Yosef Shprintzak, the chairman of the committee of the Poel Ha’Tzioni, wrote regarding the moving words of Eliezer Ungar and his friend, Yosef Korniansky: “Two men came from the inferno and shook our consciences. We must do something!”Ungar did not suffice with this. Following his first appearance, he was invited to speak that evening at the meeting of the United Kibbutz Movement, which took place at Kibbutz Givat Brenner. The Devar and Al ha-Mishmar newspapers of January 21, 1944 reported on the statements of Ungar and Korniansky at length. At that meeting, Ungar repeated his earlier statement: “Six million martyrs are no longer.” All of Polish Jewry was lost. Ungar’s speech had a powerful effect on those present.Eliezer Ungar was a staunch defender of the Jews of the ghettos, fighting against the common perception that they “went like sheep to the slaughter.” In his statement, he spoke about the revolts in various ghettos, specifically mentioning the Warsaw Ghetto Uprising: The descendants of the Maccabees demonstrated amazing courage… [This courage] will illuminate with eternal light the darkness of the days of the destruction of Polish Jewry… Anyone who thinks that the Warsaw Ghetto revolted on the eve of Passover 1943 is quite mistaken. The Warsaw Ghetto fought and struggled from the very first moment that its walls were erected. It lived and died with courage and faith in the eternity of the Jewish People. Regarding the question of why most Jews did not resist, Ungar stated emphatically: “One must experience the seven sections of Hell in order to answer that question. One who did not experience it has no right to judge. And the answer is: [They did not fight back due to] collective responsibility. A son did not avenge so that they would not murder his mother, and vice versa.”The effect of Ungar’s words was significant. The headline of the Haaretz newspaper on January 1, 1944 read: “Six Million Jewish Victims.” Is it plausible that after such a headline and the related articles, the Jews of Palestine did not know about the magnitude of the Holocaust?The question of the source for Ungar’s number is a separate question. A headline in the Devar newspaper (edited by Berl Katzenelson) from November 30, 1942 may provide a partial answer: “Six Million Jews and One Million Children are in Danger.” Apparently, six million was the number accepted in those days as the total number of Jews in Europe. Eliezer Ungar, one of the Religious Zionist leaders in Europe during the years of the Holocaust, wished to convey that this entire Jewish community had been obliterated. In January 1944, Ungar was the first – to the best of my knowledge – to cite the number six million as the number of Jews murdered in the Holocaust. The writer works at the Institute for Holocaust Studies, Bar-Ilan University and established and runs the Elie Wiesel Archive at Boston University.