Playing Mass Effect 3 again recently I got to thinking - exactly how long did the Reaper War last? Does Mass Effect 3 actually end in 2187 perhaps?
MY thinking is along the lines that in-game we are told that Earth fell months ago - this is stated by several people when you return during Priority: Earth, notably Hackett. We know Shepard spent a lot of time flying around the galaxy to stop the Reapers, and we know that as mass relay travel is not instantaneous, that took time (I'm aware the codex says the travel is instantaneous, but look at the opening scene of ME1 - the Normandy is travelling for a while.) We know that Shepard was given shore leave, because the Normandy needed repairs, suggesting the Normandy had been active on the frontlines for a significant period as well. We also know the Virmire Survivor is badly injured and spends several weeks healing. We also know the Crucible is an enormous structure that would have taken months to build.
So how long did the Reaper War last? Well Arrival takes place in early 2186, some time after ME2 and enough time for the Reapers to get almost to the galactic edge. When Arrival ends the Reapers were hours away from the Aratoht system. With the system gone, they now need to head towards the nearest system. If Arrival takes place, for arguments sake, six months after the Suicide Mission, then the Reapers could probably arrive at a Batarian system in a month, probably less.
ME3 starts with Shepard having spent six months in Alliance custody - meaning that if Shep gave him/herself up immediately after Aratoht, then the Reapers were possibly in Batarian space for 5 months. 5 months in which the Batarian race was nearly exterminated to provide the Reapers with ground troops - something that probably happens on the Citadel during every other cycle. How did this go unnoticed? Because of the Batarians seclusion they only began to admit there was a problem when Kar'shan fell, which is also when Earth was attacked.
Now with forces the Reapers would have been able to spread quickly - not having to worry too much about gathering strength. Palaven, along with many other turian and human worlds, would have been assaulted in short order. A few weeks say, during which time Shep is dealing with the Council, helping Javik, etc. Shepard probably arrives to help Victus roughly a week after Palaven is first attacked - and so we already have another month added to the timeline. Add in a few days before the meeting and raid on Sur'kesh, then another month or perhaps even longer for Mordin to create the genophage cure while Victus manages the turian front from the Normandy. In this time the VS is healing, and also gets their Spectre offer.
Then the genophage is cured, and the krogan counterattack begins. At the same time Cerberus makes its move on the Citadel. With that ended the focus of Shepard's war moves to Rannoch, and the journey there alone could have taken a week. The war there another week or so before it reaches a resolution. by this point the war could have lasted anywhere between three and 6 months. Shore leave logically fits here - taking the Normandy off active service during its return from Rannoch. Lets say a fortnight, maybe a month in drydock, before the battle reaches Thessia and other asari worlds, striking badly at the heart of their territory. From Thessia things move quickly towards a resolution - the Crucible nears completion, Sanctuary is exposed, and the fleets ready to strike at Cerberus. The thing is, this could be anywhere from 5 to ten months after the Normandy left Earth, meaning we are most likely into 2187 by this point, not 2186. After that the battle on Earth is relatively quick, but even then the impression is still made that this battle rages on for hours as Hammer readies itself to push forward, but getting all the assets together for the invasion would have taken time, as much more is taken to Earth than to Cronos Station - most likely the Alliance readied first and attacked Cronos, while the rest of the fleet prepared near the Crucible. The survivors from Cronos probably formed the Shield group protecting the Crucible, giving them the time to prepare.
What does anyone else think? How long to you imagine the war lasted?