Today, observant Jews across the world are fasting - that means no eating, no drinking. Why? The Mishnah in Taanit lists five tragic events that befell the Jewish people on Shiva Asar B'Tammuz. These events span the period of history from the year of yetziat Mitzrayim (leaving Egypt) and matan Torah (receiving the Torah) through the generations following the destruction of the second Beit Hamikdash (Temple). Unfortunately, other terrible events that have happened since the days of the Mishnah could be added to this list.
What happened on Shiva Asar B'Tammuz?
1. The Tablets were broken
Moses descended Har Sinai with the first set of Tablets inscribed with the 10 Commandments, the foundational mitzvoth or obligations of the Torah. When Moses arrived to the israelites' encampment he saw that while he had been away the Jews had lost faith and had built a golden calf, an idol. Moses was so distressed he dropped the Tablets, shattering them.
2. The daily sacrifice was suspendedin the time of the First Temple due to a shortage of sheep because of the siege around Jerusalem
3. The walls of Jerusalem were breached in the time of the First and Second Temples
The walls were breached by Nebuchadnezzar in 586 BCE and then by Titus in 70 CE. These breaches came after many months of siege in which the city's residents suffered extreme hardships, sickness and hunger.
It should be noted that during the period of the First Temple we know the walls of the city were actually breached on the ninth of Tammuz, according to statements made in the Book of Yirmiyahu. We understand from the Rambam that we commemorate this tragedy on the seventeenth of Tammuz (shiva asar) because the Jewish people were unwilling to accept two communal fasts in one month.
4. The Torah Scroll was burned
On the 17th of Tammuz, a number of years before the destruction of the Second Temple, during the time of the Roman Procurator Comenus, there was great tension between the Romans and the Jews. Josephus Flavious tells of the burning of the Torah Scroll by Comenus and his forces:
"On the royal road, near Beit Horon, robbers befell the cortege of Stephanus, a royal official, and they thoroughly plundered it. Comenus sent an armed force to the nearby villages and ordered the arrest of their inhabitants, who were then to be brought before him. It was their sin that they failed to pursue and capture the robbers. One of the soldiers seized a scroll of the Holy Torah in one of the villages; he tore it and cast it into the fire... From all sides the Jews gathered in trembling, as if their entire land had been given to the flames..." (From http://www.virtualjerusalem.com/jeisholidays/3weeks/17tamuz.htm)
5. An idol was placed in the sanctuary
Apustumus, a royal Roman official, placed an idol in the Second Temple on the 17th of Tammuz