ShalomNewYork.com

“On the tenth of Teves Nevuchadnetzar besieged Jerusalem. A siege is not as tragic an event as that for which any of the other public fast days were instituted. During the siege the city itself remained intact; the Beis HaMikdosh continued to function; and even the sacrifices continued as usual. In contrast, on the seventeenth of Tammuz the daily sacrificial service was interrupted and the city’s walls were actually breached;[9] and on the ninth of Av, the Beis HaMikdosh was destroyed. The beginning of the siege on the tenth of Teves surely cannot compare in tragedy to these events. Yet, according to one opinion, the fast of the tenth of Teves, unlike other fasts, is not postponed to another day when the tenth is Shabbos.” SichosInEnglish.org