Fasting takes place on the four following days in commemoration of the destruction of the Temple in Jerusalem: 10 Tevet, the start of the siege of Jerusalem by Nebucadnezzar; 17 Tamuz, the date of the conquest of Jerusalem; 3 Tishri, date of the murder of Gedalia, the ruler of the town imposed by the Babylonians; and 9 Av, the date of the destruction of the First Temple by the Babylonians and of the Second Temple by the Romans. Fasting on these dates is an expression of mourning. The events are historical facts, although the dates are not. 9 Av is a strict feastday: where on the other three days fasting commences at daybreak, fasting on 9 Av starts the evening before and must be observed as strictly as on Yom Kippur. There is no ban on work. Throughout the day the biblical Book of Lamentations, the Book of Job, and mourning liturgies are declaimed. This day was also used in Frankfurt to commemorate the destruction of the first Jewish community in the Pogrom of 1241, and special songs of mourning were composed for this.