A Mark II Naquadah generator used to finally activate the Ancient Control Chair, though the city's drone supply is revealed to be critically low. Friction and Failures

"The Siege: Part 2" perfectly encapsulates the high stakes of Atlantis , leaving viewers wondering if the expedition's survival was even possible.

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This friction is worsened when the high-tech defenses fail. The Wraith cleverly use asteroids to trigger the nuclear mines at a distance, rendering them useless and blinding the city's sensors with radiation. Desperate Alliances and Sacrifices

With the Wraith overrunning the city, Weir is forced into a hostage situation with the Genii to trade for prototype nuclear weapons. Back at Atlantis, Rodney McKay and Radek Zelenka work through exhaustion to complete the unfinished Genii bombs. The episode concludes on a gut-wrenching cliffhanger:

The "cavalry" isn't without its costs. Colonel Everett immediately clashes with Dr. Elizabeth Weir and John Sheppard, holding a personal grudge against Sheppard for the death of Colonel Marshall Sumner.

Railguns and Naquadah-enhanced nuclear mines deployed to intercept the approaching Wraith Hive ships.

The first season finale of Stargate Atlantis , " The Siege: Part 2 ", remains one of the most intense hours in the franchise's history. Just as the expedition prepares for their darkest hour —arming a self-destruct virus and preparing for a total evacuation—a literal light appears at the end of the tunnel: the Stargate activates with an incoming IDC from Earth. The Arrival of the Cavalry