http://revach.net/lists/article.php?id=49

Section: History   Category: Bais HaMikdash
TAGS:17 Tammuz  avodah zara  churban
5 Terrible Events That Happened On 17 Tammuz
The Mishna lists five terrible events that happened on Tisha B'Av.  The Seder HaYom says that whop cannot fall on the floor and weep from even a single one these events let alone all five.  Not all of the events are clear when and where they happened, and by who. 

1.  Chait HaEigel and The Breaking of the Luchos - According to Rashi Moshe only burned the Eigel and punished the sinners the next day on 18 Tammuz.  According to the Ramban it all happened on the very same day.

2.  They stopped bringing the Korban Tamid - According to the Yerushalmi this occurred during the Second Bais HaMikdash.  The Rambam brings that it refers to the First Bais HaMikdash.  This happened three to six years before the Churban either because the King decreed that it be abolished or because they simply ran out of lambs due to the war and strife.

3.  The walls of Yerushalayim were breached - Surely this was the date during the second Bais HaMikdash under Titus, although the date of the breach by Nevuchadnetzar in the first destruction is a matter of dispute.  Some say that it actually happened on the 9th of Tamuz as recoded in Tanach, while some say that the real date was 17 Tamuz and give various reasons why it says that it happened on the 9th.

4.  Apustamus burned the torah - He was a Greek general and he burned the special Sefer Torah of Ezra that was in the Bais HaMikdash.  Some say that he burned many sifrei torah to erase it from Klal Yisroel.

5.  An Idol was placed in the Heichal - The Rambam says that this was done by Apustamus during the second Bais HaMikdash.  Rashi says that this refers to the Idol placed by Menashe the King of Yehuda during the first Bais HaMikdash.  (See also Sefer Yisroel V'Hazmanim - Rav Dovid Rossof)