June, 2184 – Normandy SR2 marooned near Galactic Center after destroying the Collector Base.
December, 2185 – Tensions flair between the Turian Hierarchy, the Systems Alliance and the Batarian Hegemony. Points of conflict largely consist of old territorial rivalries and various reparation debts from previous conflicts that had gone unpaid. The conflict is secretly encouraged by Reaper agents, taking advantage of existing bad blood.
February, 2186 – Reaper fleet breaches the galactic plane near the Valhallan Threshold. The quarian Migrant Fleet encounters lead Reaper elements and scatters after attempts at communication result in the destruction of many quarian ships. The Reapers make for Rannoch.
February, 2186 – Reapers enter Geth space and ignore all geth attempts to engage or communicate.
March, 2186 – Reapers arrive in orbit over Rannoch and issue an ultimatum to the geth consensus: Serve us or die. The geth decline.
March, 2186 – After a rigorous battle, the Reapers successfully eradicate the Geth presence in the former quarian home system. Remaining geth strongholds go into an unprecedented full war footing.
April, 2186 – Quarian messenger ships arrive in Salarian Union space bearing news of the invasion. Most of their envoys are dismissed or arrested. However, token STG teams are dispatched to investigate.
May, 2186 – Geth messenger ships arrive in Systems Alliance space bearing news of the invasion. Most of their envoys are destroyed.
May 2186 – Conflict between the Alliance and the Hegemony escallates to something just short of full-scale war. Turian fleets confront forces from both sides and seize certain assets, identifying themselves as peacekeepers. Alliance officials accuse the turians (somewhat accurately) of profiteering and refuse to recognize turian authority.
June, 2186 – Reapers begin subduing minor species in the Terminus Systems.
June, 2186 – Significant clashes occur between human and batarian naval forces.
July, 2186 - Both sides in the human/batarian conflict engage turian forces in isolated incidents. The Turian Hierarchy initiates a full-scale mobilization, deploying fleet assets throughout human and batarian space.
July, 2186 – The Salarian Union dispatches more STG task forces to investigate unexplained disturbances within the Terminus Systems, as well as to investigate the status of the initial STG probe, which has not reported back.
August, 2186 – Turian, batarian and human forces clash in a three-way battle near Terra Nova. Casualties mount.
August, 2186 – STG units send back a report detailing the Reaper conquest of a minor Terminus race called the kahek. The Salarian government covertly raises the readiness status of its frontier fleets, alerts various secret outposts in the Traverse, and begins the large-scale deployment of STG assets into the Terminus.
September, 2186 – Reapers begin subduing the major powers of the Traverse. A desperate missive from the homeworld of one Terminus race – the norissi – reaches Thessia via FTL comm. The norissi beg the asari for aid against an invasion by an unknown alien power. FTL comm contact is soon lost. The asari prepare a humanitarian relief fleet with a robust military escort.
October, 2186 – The Council brokers a temporary ceasefire between the humans, batarians and turians, but the situation remains unstable due to an unexplained dearth of peacekeeping forces from the asari and salarians.
October, 2186 – A secret Salarian research base in the Traverse is destroyed by Reaper forces. The Salarian Union denies the facility's existence and blames several recent ship disappearances on pirates.
October, 2186 – The asari relief fleet embarks on the twelve-relay trip to norissi space.
November, 2186 – More Salarian outposts in the Traverse go dark. A naval patrol of several cruisers vanishes without a trace. The Salarian Union mobilizes its fleets, which draws the attention of galactic news networks. The turians withdraw a third of their deployed fleet strength to their home systems, sensing trouble. Sporadic combat breaks out between batarian and human fleets.
November, 2186 – The asari relief fleet executes the final relay jump on its itinerary and is never heard from again.
December, 2186 – Large, ramshackle refugee fleets begin arriving in Salarian space, fleeing what the Salarian government calls “unspecified conflict”. The Salarians keep their borders closed, fearing indoctrinated agents, and are rebuked by the other council races for their callousness.
December, 2186 – The volus, elcor, hanar and other council races muster their fleets and armies in response to galactic instability. The Hierarchy insists that the volus stand down, not wishing to add any additional hostile parties to the fraying galactic situation. The volus begrudgingly accede.
January, 2187 – Massive Reaper fleets breach Salarian and Asari territory simultaneously. Several colony worlds burn before anything can be done.
January, 2187 – An asari fleet is severely mauled during a brief engagement with a Reaper. This knowledge is concealed. The missing ships are said to be out on maneuvers.
February, 2187 – A Salarian fleet is destroyed trying to defend a mid-sized colony from several Reapers. This knowledge is concealed. Colonial disturbances are blamed on pirates.
February, 2187 – Panic erupts throughout Citadel Space as an intrepid reporter returns from the chaos of the Traverse bringing knowledge of the invasion. Authorities successfully restore order, describing this as the incursion of a new, unidentified race which would be brought to heel soon enough.
March, 2187 – The Asari and Salarians lose several more colony worlds.
March, 2187 – The scale of the threat becomes increasingly common knowledge as more footage emerges from falling colonies. The Council admits that it faces a full-scale invasion. The turians immediately withdraw more forces from human/batarian space.
April, 2187 – The fleets and armies of the Asari Republics gather at the threatened colony of Lnea, in all of their splendor. The Matriarchs vow that the coming battle will demonstrate that this new enemy can be beaten, and beaten decisively.
April, 2187 – The Reapers arrive at Lnea and quickly break the asari resistance. Panic erupts at the news. The asari navy is crippled. On the ground, two hundred thousand asari warriors have been slain in an afternoon, far more than were lost during the entire first century of the Rachni War.
May, 2187 – Peace between the Alliance and the Hegemony, who begin refitting their fleets and mustering reserves.
May, 2187 – The Salarian Union, their military reeling, invokes the direst of contingencies. Secret seals are broken and encryptions are read. A number of incredibly-illegal drone fleets emerge from secret bases on the salarian frontier. Prohibited weapons are retrieved from deep vaults. Atomics, vicious bio-weapons and illegal, military-grade AIs are planted on worlds thought to be in the path of the Reaper advance. Some minor citadel races protest these methods, but are ignored. Much of the remaining asari military – now fragmented – refuses to cooperate with the Salarians on future ventures due to the dishonor of Salarian tactics, but a few republics order their contingents to cooperate, under protest.
May, 2187 – The Reaper advance is stalemated on several Salarian colony worlds, as prohibited devices and asari support help the threadbare salarian infantry delay Reaper harvesting operations.
May, 2187 – Two turian fleets arrive in Salarian space, reinforcing the Union Navy.
June, 2187 – The Salarian Navy counter-attacks along a broad front, taking advantage of the Reaper stall. Simultaneously, their secretive elements make for the exposed rear of the Reaper advance. The Reapers are enveloped.
June, 2187 – The Reapers easily break through the Salarian/Turian envelopment and force the Salarian navy into rout. The Turian fleets, along with the few asari vessels that have remained attached, refuse to retreat and are eradicated. Much of the Salarian drone fleet, along with many AIs, are subverted and come under Reaper control.
July, 2187 – Effective resistance to the Reapers in Salarian and Asari space ends. Mass panic ensues throughout the galaxy, as both asari valour and salarian cunning have failed to halt the invasion.
July, 2187 – The Salarian Union enacts its apocalyptic protocols, sending key personnel and resources to wait out the war in secret holdfasts, some of them outside the galactic plane. Asari military leaders refuse all invitations to join in this process and focus on the consolidation of assets and populations in turian space.
August, 2187 – 95% of the remaining asari military is destroyed attempting to defend evacuation convoys.
August, 2187 – Thessia goes dark.
September, 2187 – Sur'Kesh goes dark.
September, 2187 – The Reaper invasion fleets converge and make straight for Palaven.
September, 2187 – Black Watch operatives report Reaper movements. Turian fleets amass at Palaven, joined by most of the remaining military might of the Council races. The turians mobilize their reserves.
October, 2187 – Reaper forces enter the turian home system and find themselves facing eleven thousand warships – half of them turian, the rest batarian, human, volus, elcor, hanar and others – along with hundreds of orbital defense platforms, tens of thousands of fighters, millions of mines, drones and missile pods, and six hundred million turian soldiers entrenched on the most heavily-fortified planet ever known to exist.
October, 2187 – Scattered remnants of the allied fleet flee Palaven after three days of battle.
October, 2187 – Palaven goes dark.
November, 2187 – Irune goes dark.
November, 2187 – Dekunna goes dark.
November, 2187 – Earth goes dark.
November, 2187 – Khaje goes dark.
November, 2187 – Khar'shan goes dark.
January, 2188 – The Normandy SR2 returns to Citadel Space.