During the Tau'ri-Goa'uld War a group of Goa'uld who saw the corrupting and weakness of the System Lords, acted by manipulated their worlds, delayed shipments of goods and materials, corrupted data and coordinates, and without discovery, unwound the old System Lords.
In the void that was left after the fall of the Goa'uld Empire, this group of Goa'uld had self-appointed themselves as System Lords and had secretly collected worlds unknown to the Tau'ri and their allies. Ancient worlds long forgotten by the old System Lords, as the bases from which they planned their ascendance for a thousand years.
Just over a year after the death of the last System Lord, Ba'al and two years since the death of the Ori. The new System Lords had seemed to have rallied sometime in between 2008 and 2010 and started organized assaults and conquering key locations throughout the galaxy in 2010 in order to re-enslave the human populations that the Tau'ri had freed, they also plan to attack Earth, the heart of humanity.
On Amarna, Stargate Command had landed a force on this world to investigate a naquadah mine which they thought to be abandoned. The Goa'uld had quickly learned of the SGC's trespass and sent a formidable task force to secure both the Stargate and their precious naquadah, the principle power source for all Goa'uld technology. As the SG-Team makes their way back to the Stargate to check in, to their surprise, they find the temple that houses the gate crawling with System Lords forces. They now have a serious fight on their hands and must stop the enemy incursion just to make it home. Later Leonops was visited by the Tau'ri of Stargate Command who were scouring the planet for Mahes resurrection technology. Whilst on the planet, they accidentally entered into the Court of Judgment and triggered the games. They were shortly joined by forces from the System Lords Third Battle Group, both groups battling to the death repeatedly before the Tau'ri eventually won. Both sides left the planet shortly after, alive only due to Mahes technology.
On Piramess, a weather control technology could potentially be used as a weapon on other worlds, and the Goa'uld have taken notice of a weather control device that was devised that keeps the temperature warm within the confines of their temple cities on Piramess, which was sought by the Goa'uld who descended upon Piramess from orbit, using the weather control device to freeze the capital cities. With such a device, they could force hundreds of worlds into submission. However, forces of the Tau'ri have arrived to restore Piramess planetary defenses and drive the Goa'uld away.
The Goa'uld had finally obtained a viable transmission key, allowing them to pass through Earth's Stargate and establish a firm foothold inside Stargate Command. They have already disabled primary iris control, assassinated all commanding officers capable of detonating the SGC's fail-safe device, and must now defuse the device itself to ensure safe passage for the legions of their brethren waiting to enact furious devastation on the Tau'ri's home world. The SGC's reserve forces have been called in to repulse this attack. Goa'uld forces secured the Stargate but not control of the fail-safe device: a massive explosive capable of flattening the facility; but the Tau'ri stave off the Goa'uld should their mission fail. Which they managed to do and pushed the Goa'uld off-world. (Stargate Resistance)