Previous:	Theshaca Raids
Concurrent:	Quarian-geth conflict Krogan Civil Wars Hegemony slave wars Anhur Civil War War on Taetrus
Next:	Second Skyllian Cold War
Reaper campaign Part of the Galactic Harvest
An artistic interpretation of Shepard's struggle to save the galaxy during the Reaper War.
Date:	9 June 2183 CE - 24 September 2186 CE (3 years, 3 months and 16 days)
Location:	Galaxy-wide
Outcome:	Decisive UGC victory Reapers are completely wiped out Dissolution of Cerberus End of the Galactic Harvest Galaxy is irrevocably changed politically, militarily, socially, technologically and economically
Engagements:	Eden Prime War Post-war Heretic conflict Collector campaign War for the Corpse First War for Omega Bahak Incident Reaper War Second Morning War Second War for Omega
Belligerents Systems Alliance (2183 CE) Cerberus (2183 CE - 2185 CE) United Galactic Confederacy (2186 CE) The Reapers (2183 CE to 2186 CE) Saren's Alliance (2183 CE) Prothean Collectors (2183 CE to 2185 CE) Cerberus (2185 CE to 2186 CE) Commanders Marcus L. Shepard † Tali'Shepard Steven Hackett Adrien Victus Hundreds of other commanders over the course of the campaign. Sovereign † Harbinger † Great Intelligence † Collector General † Saren Arterius † Hundreds of other commanders over the course of the campaign. Illusive Man † Kai Leng † Randall Ezno † Oleg Petrovsky Dozens of other commanders over the course of the campaign. Strength 3.2 billion total military forces by campaign's end 217,589 ships 9.8 trillion husks of varying design by war's end 6 million Prothean Collectors Geth Heretic Army 60,000 troops 6,000 aircraft 300 tanks Geth Heretic Navy Fleet of the Herald 320 ships Heretic Reserve Fleet 113 ships Indoctrinated forces 23rd Commando Company 700 tank-bred krogan Entirety of the Cerberus Armed Forces Casualties Nearly catastrophic Complete obliteration of all forces Near total destruction of Cerberus

"The Reapers are coming. They're bringing hundreds of ships, maybe thousands...I'm going to find some way to stop them. The war doesn't end here. Sovereign was just a vanguard...a beginning. Many more like him are coming for us all, and I'm going to need all the resources you can spare if I'm going to find a way to defeat them."

— Marcus L. Shepard to the Citadel Council following the Battle of the Citadel, emphasizing the extent of the Reaper threat.

The Reaper campaign, sometimes called Shepard's War and later known as the Great Cyclic Wars, were a series of conflicts during the asari cycle from 2183 CE to 2186 CE, spearheaded by Marcus L. Shepard, that aimed to stop and destroy the Reapers, and to break their cycles of galactic destruction once and for all, but also contextualizes and encapsulates all conflicts occurring during this period involving the Reapers. Three main conflicts comprised the campaigns, beginning with the Eden Prime War, escalating with the Collector campaign, and concluding with the Reaper War. Other conflicts are also considered to have contributed to the overall campaigns, such as the first and second wars for Omega, the Bahak Incident and the Second Morning War: to some degree, due to Reaper influence, the Rachni Wars are unofficially considered part of the campaign as well, although the conflict is chiefly remembered for Shepard's personal involvement.

The Reaper campaign began with the Battle of Eden Prime on the 9th of June 2183 CE. Due to the Citadel Council's denial of the Reapers' existence, Shepard and his team were largely left to fight the conflict themselves, utilizing their own resources and leads to hamper Reaper efforts to invade the Milky Way Galaxy, with their second attempt at opening the Citadel relay having been thwarted by Shepard at the Battle of the Citadel. When this effort failed, the Reapers switched tactics and gave up trying to come through the relay, and turned their attentions to the Alpha Relay. While this occurred, Harbinger turned his attentions to humanity, believing them to be a threat. He unleashed the Collectors on the galaxy early, directing them to kill Shepard and destroy the SSV Normandy SR-1 and, once that was done, to begin abducting human colonies. The Collector campaign began with momentous Reaper success, with Shepard killed, his ship destroyed and crew scattered, leaving the Collectors free to conduct their new orders unmolested. Things fell apart when Collector efforts to retrieve Shepard's body failed, Cerberus obtaining it and later resurrecting Shepard after an extraordinarily expensive procedure that took two years. Within the same year, Shepard had reassembled parts of his old team, formed a new one, gained a new ship, and eventually defeated and obliterated the Collectors at the Collector Base Assault in October 2185 CE. With his third plan having failed, and another of their assets lost, Harbinger put all efforts on reaching the Alpha Relay to begin their invasion.

This effort was again thwarted by Shepard at the Bahak Incident, when he destroyed the Alpha Relay by slamming an asteroid into it: this wiped out the entire system, killing three hundred thousand batarian colonists, but delayed the Reapers by another six months. This effort was in vain however, as Shepard was placed under house arrest and his squad once again scattered due to growing tensions with the Batarian Hegemony over what they perceived to be a terrorist attack, and at worst, a declaration of war. As such, no preparations were made, and with nothing left to stop them, the Reapers invaded in June 2186 CE. The Reaper War lasted just over three months, and brought an end to the Reaper campaign with the complete destruction of the Reapers, but the cost was in tens of billions of lives.

The Reaper campaign was one of the most important conflicts in Milky Way history, if not the most important due to its lasting effects on the future going forward. With the cycles no longer being enforced, galactic society was free to advance and thrive without the restriction of a Reaper cycle, and while this was celebrated by those who had survived the Reaper apocalypse, it also had the consequence of much larger, more devastating wars being fought in the decades that followed.