Previous:	Hijacking of the SSV Normandy
Concurrent:	Battle of Ilos
Battle of the Citadel Part of the Eden Prime War
CDF ships engage Sovereign and the geth fleet in the opening stages of the battle.
Date:	19 July 2183 CE
Location:	On and around the Citadel / Widow / Serpent Nebula
Outcome:	Decisive Council/Alliance victory Sovereign is destroyed, and Saren Arterius killed CDF suffers heavy losses Citadel is severely damaged Fleet of the Herald decimated, rest forced to retreat Complete military defeat of Saren's Alliance Humanity gains a seat on the Council Eventual Reaper invasion delayed for three years End of the Eden Prime War
Belligerents Citadel Council Systems Alliance (joined late in the battle) Saren's Alliance Geth Heretics Commanders Lidanya V'mosus Ulik Gagas † Venari Pallin † Marcus L. Shepard Steven Hackett Saren Arterius † Sovereign † Strength Citadel Defense Forces Citadel Defense Fleet 132 ships 1 Vanguard-class dreadnought THS Iron Conviction 1 Ascension-class dreadnought ARW Destiny Ascension Citadel Security 50,000 personnel Systems Alliance Navy Fifth Fleet 382 ships 1 Kilimanjaro-class dreadnought SSV McKinley 1 Normandy-class stealth frigate SSV Normandy SR-1 Systems Alliance Marine Corps 6,000 marines Normandy Squad 6 combatants 1 M35 Mako Geth Heretic Army 20,000 geth troops 1,000 geth recon drones 2,000 geth assault drones 11,467 geth troopers 2,000 geth destroyers 2,000 geth juggernauts 1,000 geth hoppers 300 geth primes 1,000 geth armatures 300 geth colossi Geth Heretic Navy Fleet of the Herald 320 ships 1 Sovereign-class Reaper Sovereign Casualties 70 CDF ships destroyed, 21 damaged 12,000 C-Sec troops killed 130 Alliance ships destroyed, 78 damaged 1 Mako destroyed 800 marines killed Thousands of civilian casualties Death of C-Sec executor Total destruction of geth ground forces 298 ships destroyed, 10 crippled Sovereign destroyed Saren Arterius killed

"Heroes of the Citadel: Eternal is their sacrifice, clear is their reflection."

— Inscription on the "Heroes of the Citadel" monument built in memoriam of the Systems Alliance personnel who gave their lives during the Battle of the Citadel.

The Battle of the Citadel, sometimes but rarely called the Battle of Widow and known to Saren's forces as Operation Catch Cry: Phase II, was the climatic engagement of the Eden Prime War, and the largest confrontation of the entire conflict, fought between the forces of Saren's Alliance and the Citadel Council, with Systems Alliance reinforcements arriving later in the battle. The battle saw the largest deployment of forces seen throughout the war, and was intended as the knockout blow that would win the war for Saren's forces and bring about the return of the Reapers. The battle took place in two phases: while Sovereign and the Fleet of the Herald launched a surprise naval assault on the Citadel Defense Fleet, knocking them out and allowing Sovereign to enter the Citadel, Saren Arterius and their ground forces would use the Conduit on Ilos to board the station clandestinely, overwhelming C-Sec and securing control of the station for Sovereign to open the portal. Saren's Alliance committed their remaining resources to the operation, and for the first time in the entire conflict, Sovereign would take an active role in the battle, effectively coming out of hiding for the first time in the war.

The battle went poorly for the Council in the initial stages. Taken completely by surprise, the Fleet of the Herald destroyed the few ships guarding the Hector relay and blitzed into the Widow system, quickly opening up with a large salvo that pulverized and obliterated the unsuspecting forward lines of the CDF, who were not at all combat ready. Twenty percent of the CDF was knocked out immediately, with the rest rallying quickly behind their two dreadnoughts, the THS Iron Conviction and ARW Destiny Ascension. Meanwhile, on Ilos, the Normandy Squad was unable to stop Saren and his troops from reaching the Conduit, and Saren's troops quickly overran C-Sec's tactical teams, clearing a path to the Citadel Tower for Saren to advance. Saren successfully gained control of the station, and Sovereign, after destroying the Iron Conviction and leaving his geth to mop up the CDF, entered the Citadel, Saren closing the arms behind it. Victory was seemingly assured for Saren's forces.

However, upon the second phase of the engagement, the SSV Normandy turned itself into the Alliance authorities near the Armstrong cluster, where Jeff Moreau was instructed to warn Admiral Steven Hackett of the impending attack. Alarmed by this news, the Normandy was allowed to rejoin the Fifth Fleet and Hackett immediately ordered for all ships to mobilize and "force march" to the Citadel. On the Citadel itself, the Normandy squad pushed through geth forces left to defend the Conduit and arrived on the station, quickly catching up to Saren, despite his attempts to stop them. After a tense confrontation, Saren freed himself of Sovereign's control enough to kill himself. Commander Shepard reassumed control of the station, doing so just as Hackett's fleet arrived to reinforce the CDF. With orders to save the Ascension and the Council, the Fifth Fleet blitzed through the relay and smashed right on top of the geth fleet, obliterating it in the initial salvo with minimal casualties. The Alliance ships then immediately engaged Sovereign. The battle lasted for another twenty minutes, with the Alliance suffering heavy casualties trying to destroy Sovereign. Thankfully, the destruction of a huskified Saren crippled Sovereign, allowing Hackett's remaining ships, and the rallied CDF, to finally bring Sovereign down. Their leaders dead, the geth fled the system, and all organized resistance collapsed. The battle was over, and with it, the Eden Prime War.

The Battle of the Citadel has a longstanding legacy, and is considered one of the most decisive conflicts in galactic history. Already famous due to his actions on Elysium seven years earlier, Shepard was risen to galactic hero status, branded the "Hero of the Citadel". The Alliance were seen as heroes, particularly those personnel in the Fifth Fleet, and humanity was finally granted a seat on the Citadel Council for their role in defeating Sovereign. For a month, the Council secretly acknowledged the Reaper threat, although this stance would be reversed after Shepard's death in an ambush over Alchera, with Sovereign officially identified as a geth superdreadnought. However, the damage had been done: many could no longer deny the Reaper threat, and limited scale preparation for a future war with them began to mount.