Battle of Tazek'sur
From The Stargate Omnipedia
A battle on Chulak in which Gerak's father was a major player. During this battle many Jaffa fought for their freedom from the Goa'uld, but they would ultimately fail. However, this battle was key to instilling serious doubt in Gerak's mind that the Goa'uld were gods.
KEY EPISODE
The Fourth Horseman, Part 2 - Teal'c brings Gerak to the site of the Battle of Tazek'sur to remind the Jaffa-turned-Prior that he cannot destroy his brethren.