At the climax of Anathem, the members of Cell 317 conduct an attack on the Daban Urnud to disable the Worldburner.
The attack begins with the members of the cell launched into space using an old mobile ballistic missile launch system with special payloads consisting of a spacesuited astronaut in a special booster second stage dubbed a Monyafeek by Jules Verne Durand.
The timeline of the battle is not simple, because the story tells several versions of the battle which take place in alternate worldlines in the Polycosm. The multiple worldlines are experienced because of the presence of Fraa Jad, an Incanter with the ability to experience multiple worldlines or Narratives at once, and to select among them for himself and his compatriots. The Arbrans are victorious, but only because Jad essentially made several different versions of the battle true at once.
All versions 
Edit
In all versions of the battle, the launched cell members assemble behind decoy balloons and recover a nuclear generator to power their ascent to the Daban Urnud. They set out a decoy ship which explodes to distract the observers on the Daban Urnud. They then hide behind a large mirror, and use an electric tether to match the ship's orbit. During the tether-powered orbit-synchronizing maneuver the cell is dramatically isolated it becomes reasonably clear that something unusual is happening related to the dreaming of the cell and the knowledge that ground crews have about them due to potential computer malfunctions on Arbre. In conversation they note that sometimes they are dreaming and sometimes not, with uncertainty about which events and conversations are occuring in dreams and which are "actually happening". In some dreams, some team members did not survive the launch.
The Avout have each swallowed a large pill, told that it is an internal temperature sensor. In fact they deduce that it is an Everything Killer, and that they appear to be on a suicide mission.
Once at the ship, Avout from the Ringing Vale attack the Worldburner, which appears to be being prepared for use. Other Avout, including Erasmas (accompanied by the Laterran Jules Verne Durand), attempt to enter the ship via an observatory. The Valers have success in their attack on the Worldburner, but suffer various outcomes.
The story eventually settles on one Narrative, where the crew of the ship, frightened by the attack, make peace with the people of Arbre and a ship is sent down to bring up a delegation from the planet, which also brings food and Arbre-physics oxygen for the surviving members of Cell 317.
Final Narrative with Jad Absent Edit
After the battle is concluded, almost all memories and records describe only one Narrative. In this Narrative, Jad was unconscious and was not rescued after launch. He burned up on reentry into the atmosphere. The Valers fought a proud battle to destroy the Worldburner. One was killed fighting off five workers armed with plasma torches. The rest captured a large crew in the control center for the Worldburner, which the others on the Daban Urnud took for a hostage taking. Eventually the room was retaken and the Valers were killed, but fear of the attack led to the peace agreement.
The rest of the members of Cell 317 became unconscious after running out of Arbre air and breathing ship air. They were captured and placed into a cold hibernation. They were revived when the delegation from Arbre arrived.
The members of Cell 317 remember events differently from most of those on the planet and on the ship. In particular, Erasmas remembers several Narratives (though there is a mention of at least one Narrative in which he and Jad are dead, which Jad mentions but Erasmas doesn't experience firsthand). Others presumably remember only Narratives before they parted company from Jad. This is because it is only possible to "track a narrative" within which one is alive.
At the peace negotiations, Erasmas asks Lodoghir if there was a way to bring Jad back. He replies "not without undoing that," referring to the peace treaty. This is presumably because there are no Narratives containing both a successful peace treaty and and a surviving Jad. Lodoghir could alter the past in such a way that he could resurrect Jad, or Orolo or Lise for that matter, but he could not do so without closing off all Narratives in which peace was obtained and the Everything Killers were not deployed.
Jad and Erasmas survive the Observatory Edit
Members of the cell rescue Jad when he is unconscious after launch. Erasmas recovers the nuclear reactor necessary for their mission, spending two orbits with it.
In several timelines, Erasmas finds himself alone with Jad after passing out from breathing the hard-to-metabolize air of the Daban Urnud. Jad informs Erasmas that he is experiencing several Narratives. In this one, the other members of the cell are dead, and they must go forward. Erasmas is informed that in other Naratives where his friends are alive, Erasmas is dead or "absent."
They explore the ship and come to a control panel for the ball valve into one of the orb habitats.
Jad keys in the correct code Edit
In one Narrative, Jad keys in the correct code and they enter the orb. Soldiers attack them and shoot them. As a final act, Jad uses his special Jeejah to detonate the Everything Killers, killing them and many on board the ship.
Jad keys in an incorrect code Edit
In at least one Narrative, Jad does not open the ball valve, and they are captured and taken to meet the Gan (Admiral) of the ship. There they discuss the history of the ship, the message received by the ship at the time of the Third Sack and the politics. They also learn the fate of the Warden of Heaven. Presumably due to strain on Jad, Erasmas' memories of this Narrative end at this point.
Another possible conclusion is that this timeline was Jad's original mission, to gather intelligence on the Daban Urnud, its people, and history. The power of the Incanters to explore the polycosm, combined with the power of the Rhetors to alter records and memories means that the two working together can explore all possible polycosm timelines. Once Jad and Erasmas found a timeline that reached the Gan, Jad used Erasmas as an amaneunsis, explaining:
"An amanuensis is more than a recording device. An amanuensis is a consciousness-bearing system, and so what it observes in its cosmos has effects in others, in the manner we spoke of at Avrachon's Dowment."
Essentially, Jad was using Erasmas as a conduit to pass the information he gleaned from the Gan to other Incanters and Rhetors on Arbre (most likely led by Lodoghir). Once they had pulled all of the information they felt was relevant from the Gan, the Rhetors reversed the course of time and brought about the Final Narrative timeline that we see as the end of the book (where Jad dies). However, because Erasmas and his friends had direct interaction with Jad in the timelines where he lived, the Rhetors were incapable of wiping away all memories of those events, thus explaining the disjointed memories all of the main characters have of Jad living.
Who died during the launch, and what happened to the radio link? Edit
During the tether-driven orbit matching, some members of Cell 317 report that their own ground based controllers believe them to be dead. This suggests that from the perspective of the ground, there are Narratives where various members of the Cell, not simply Jad, do not survive the launch. Samman explains how plausible-but-false data could propagate through their reticules but very little is seen of Narratives where fewer people survived the launch. This hint in the book suggests that the Ret itself might function as a non-biological "consciousness bearing" amanuensis, which has implications throughout the book in terms of the design of social insitutions to increase the causal separation of Thousanders from the rest of the world... providing another possible explanation for segregating Ita from the avout.
In Narratives where Jad survives, he destroys their radio link with the ground. This stops reports on any conversations in which they say certain keywords from being sent to the ground, and may also serve to sever causal links with the ground, making Polycosmic Manipulation easier for Jad. In the same period, while discusing their dreams, Arsibalt mentions that he had a dream where he destroyed the radio link. The reader is never actually shown the details of such events, but it is plausible that Jad had conversations with cell members in Narratives where was present such that they performed naively deranged-seeming "dream inspired" actions in Narratives where he was absent, like destroying the radio link. The fate of the radio link in the Final Narrative is never precisely specified.
