Citadel Fleet
From Mass Effect Wiki
The Citadel Fleet is the main space defense force of the Citadel Council. The flagship of the fleet is the asari vessel Destiny Ascension, which carries almost as much firepower as the rest of the fleet combined. The Citadel Fleet consists of a mixed group of turian, salarian, and asari vessels, though the greater number of them are turian, due to the turians' peacekeeping role.
The exact number of ships in the Citadel Fleet is unknown, but there were enough vessels to patrol every mass relay linking Citadel space to the Terminus Systems and still leave enough stationed at the Citadel to provide a garrison. Ambassador Udina also claimed that the Citadel Fleet was large enough to secure the entire Attican Traverse if the Council wished.
As an agent of the Reapers, Saren Arterius, allied with the Reaper dreadnought Sovereign, launched a surprise attack against the Citadel. During the attack, the Destiny Ascension ordered Citadel control to close the station's Wards, creating an impenetrable fortress. However, Saren had used the Conduit to infiltrate the Citadel and shut down both the Citadel and the Mass Relay network, subjecting the fleet to the full force of the geth attack and preventing any reinforcements from arriving. Sovereign then broke through the fleet and closed the Citadel's Ward arms behind it.
The Destiny Ascension managed to evacuate the Citadel Council but was unable to fight her way through the hordes of geth ships accompanying Sovereign. Commander Shepard eventually reactivated the Mass Relays, allowing the Alliance Navy and the Normandy to aid what was left of the Citadel Fleet. It was then up to Shepard to decide whether to have the reinforcements save the Council and the Destiny Ascension, or to let them die while they waited for the Ward arms to reopen.
[edit] Aftermath
The fate of the Citadel Fleet ultimately depends on your Paragon or Renegade choices...
If you choose to save the Council, then it is known that at least the Destiny Ascension survives. It is not known how much of the rest of the fleet survived.
If you let the Council die, then it is implied that almost the entire fleet is destroyed.
