The Fall of Dakara occured in 2006 after the events on the abandoned Ori ship at the hands of Adria.
Prelude
The people of a world that had succumbed to the religion of Origin were all mysteriously wiped out by an unknown force. As SG-1 investigated, they discovered that the Dakara superweapon was responsible and decided to investigate further, only for things to take a turn for the worse when they met a group of Jaffa who have plans for commandeering an Ori warship and matters are further complicated when Adria returns, hellbent on finding out who or what killed her new followers.
Fall of Dakara
As SG-1 was beamed off the Ori warship and the Odyssey jumped into hyperspace to avoid the wavefront of the superweapon which the Jaffa deployed in a last ditch effort against the incoming warship as Adria took control and planned to used the ship to destroy the superweapon on Dakara in order to wipe out most of the Free Jaffa Nation leadership and population.
A desperate defense was set up by the Jaffa, although it only succeeded in killing their own warriors aboard the Ori ship, since Adria was immune to the superweapon. Eager to destroy the only real threat to the Ori, Adria fired the warship's beam weapon directly at the superweapon which completely annihilated it and the mountain that housed it. Dakara was then taken over by the Ori with little to no problems. (SG1: "Counterstrike")
Aftermath
Back at the SGC, SG-1 received word that not only had Dakara been devastated but five more planets have fallen to the Ori and the Free Jaffa Nation was thrown into disarray. With the Dakara superweapon destroyed and the Ori continuing to convert countless planets, Merlin's anti-Ori weapon was now needed more than ever. (SG1: "Counterstrike")
This also affected System Lord Ba'al plan for use of the weapon to regain his formal power base, forcing them to also seek out the anti-Ori device to defeat the Ori. (SG1: "The Quest, Part 1", "The Quest, Part 2")