This Halacha is an excerpt from our Sefer
The five tragedies that occurred on Tisha B’av:
- On Tisha B’av of year 2449 the Meraglim returned and it was decreed that the Jewish people in the desert would not enter Eretz Yisrael.
- On Tisha B’av of year 3338 [שלח-422 BCE] the first Temple was destroyed.
- On Tisha B’av of year 3828 ]68 CE] The second Temple was destroyed.
- On Tisha B’av of year 3881 or 3901 The city of Beitar was destroyed.
- On Tisha B’av the city [of Jerusalem] was plowed by Turnus Rufus.
Other calamities associated with Tisha B’Av:
- The First Crusade officially commenced on August 15, 1096 (Av 24, AM 4856), killing 10,000 Jews in its first month and destroying Jewish communities in France and the Rhineland.
- The Jews were expelled from England on July 18, 1290 (Av 9, 5050).
- The Jews were expelled from France on July 22, 1306 (Av 10, 5066).
- The Jews were expelled from Spain on July 31, 1492 (Av 7, 5252).
- Germany entered World War I on August 1–2, 1914 (Av 9–10, AM 5674), which caused massive upheaval in European Jewry and whose aftermath led to the Holocaust.
- On August 2, 1941 (Av 9, 5701), SS commander Heinrich Himmler formally received approval from the Nazi Party for “The Final Solution.” As a result, the Holocaust began during which almost one third of the world’s Jewish population perished.
- On July 23, 1942 (Av 9, 5702), began the mass deportation of Jews from the Warsaw Ghetto, en route to Treblinka.
 Mishneh Taanis 26b
 Seder Hadoros; See Gittin 88a and Rashi on Vaeschanan that we were exiled 850 years after entering Eretz Yisrael, and we entered Eretz Yisrael in the year 2488.
 Seder Hadoros; See Rashi Avoda Zara 9a
 Seder Hadoros