Yom HaShoah -- was the Holocaust unique among Jewish tragedies?

Last year I raised the question of whether the Shoah was unique among Jewish tragedies or "just" one more event on the long list of Jewish tragedies that began with the churban and continued through crusades, inquisitions, pogroms. Those who would argue against establishing a seperate Yom haShoah would most likely take the latter view, e.g. R' Soloveitchik held that 9 Av is the day of mourning for all Jewish tragedies down through the ages and the Shoah should be mourned in that context. Before this year I had not been aware that the Piecezna Rebbe, R' Klonamus Kalmish, who died in the Warsaw Ghetto, clearly took the former position. He writes in Aish Kodesh (Chanukah 1942) that he cannot understand why a Jew who learned in gemara or Midrash of the great Jewish tragedies and was untroubled by questions of faith now finds himself in religious crisis, "for those who say that suffering like ours never happened to the Jewish people are mistaken, as in the Churban and destruction of Beiter there was similar suffering..." That line is footnoted with the following -- "This applied to the sufferings we saw until 1942, but based on my knowledge of Chazal and Jewish history, the abnormal suffering, the abnormal and evil death which the evildoes have created and brought upon the Jewish people from 1942 onward, is unprecedented. May G-d have mercy and save us speedily." The footnote is dated Erev Shabbos Kodesh, 18 Kislev. The fact that this appears as a footnote, that there is a "hava amina" and a "maskana" to this discussion, is itself fascinating, but more over, we should not forget the context of the quote -- are questions of faith justifiable in light of the Holocaust? The Piecezna in the body of the text does not offer easy answers to the question of theodicy -- the comfort he offers is the historical lesson that our people have survived and outlived past suffering in many other circumstances with unwavering faith. The footnote is an acknowledgment that this faith which stood us in good stead in coping with past suffering is perhaps alone insufficient when considering the unique persecutions of the Holocaust.