The 20th of Sivan has the unfortunate distinction of being a day replete with tragedies in Jewish history and a date that was traditionally set as a day of reflection and prayers commemorating those tragedies. In 1171, one such horrific tragedy befell the Jewish community of Blois, France. A gentile servant of a local ruler reported seeing a Jew toss a murdered non-Jewish child into the Loire River. Despite there being no witnesses corroborating his testimony, no parents reported a missing child, and no corpse ever produced, the Jews of the town, numbering some 40 people were rounded up and tortured.
Forced to decide between baptism and death, they chose to die al kiddush Hashem, and on the 20th of Sivan (May 26, 1171), 32 Jews, 17 of them women, were burnt at the stake. This was the first known blood libel to occur in Christian Europe which resulted in the murder of Jews, and the effects of this horrific act were widespread and long-lasting. Rabbi Yaakov ben Meir Tam (Rabbeinu Tam) decreed the 20th of Sivan from this point forward as a fast day for Jews living in France, the Rhineland (Western Germany) and England.
Following the Chmielnizki pogroms in 1648-49, the Vaad Arba Aratzot (Council of Four Lands) reinstated the 20th of Sivan as a fast day to commemorate the pogroms and suffering the Jewish community underwent during this period. Rabbi Yom Tov Lipmann Heller, the Tosafot Yom Tov, decreed that the selichot originally composed for the martyrs in Blois, France, be recited on the 20th of Sivan to commemorate the Chmielnicki pogroms as well.
A poignant, scarce publication I acquired this week, published in Budapest immediately after the Holocaust, contains selichot for the 20th of Sivan to be recited in memory of the Holocaust victims. As soon as the enormity of the horrors of the Holocaust became apparent, there was a movement to impose a worldwide day of fasting and prayer for the victims.
R. Chizkiyahu Mishkovski, the rosh yeshiva in Kfar Chasidim, already in 1945 beseeched the Moetzet Rabbanim in Eretz Yisrael to create such a fast day. While many prominent members of the rabbinate, such as the Vizhnitz and Sadigura rebbes, were agreeable to the idea, others, including Rav Yitzchok Zev Soloveitchik and the Chazon Ish, were hesitant to create a permanent fast day, as they were of the opinion that we don’t have the ability to impose permanent fast days on the entire nation once the Temple was destroyed.
While in Eretz Yisrael a consensus did not emerge, in Hungary immediately after the war the Orthodox Rabbinate unanimously agreed to commemorate the Holocaust and the destruction of the Jews of Hungary on the 20th of Sivan every year. Their halachic argument was based on the fact that this was already an established fast day, established centuries earlier by Rabbenu Tam and reestablished after the Chmielnicki pogroms. Indeed, this publication from 1946 Budapest, Hungary, notes the 20th of Sivan as a commemoration of both tragedies.