Why was a fast instituted on עשרה בטבת

From All: R Josh Blass by R Josh Blass.

• Published: 2015-12-21T00:00:00Z
• Duration: 15:30
• Audio: https://shiurim.yutorah.net/2015/26065/847251.MP3
• Page: https://yutorah.org/lectures/847251
• TorahApp: https://torahapp.org/share/p/YU_80253_all/e/yu%3A847251