This is the hardest trophy in the game and the only trophy that requires you to play multiplayer (unless you decide to spend hours on Galaxy at War or Mass Effect Infiltrator).
Galaxy at War can be found here -
http://social.bioware.com/n7hqMass Effect Infiltrator is a game that can be found on Windows Phone or an iGadget (iPhone, iPad, etc)
In order to pop this trophy, you have to raise each theater of war from 50% to 100%. In order to do so you need to play multiplayer (or the games listed aboves).
There are five theaters of war that need to be raised to 100%. The most effective way is to do Bronze missions in each theater until you reach 100%. The maps take around 10 to 25 minutes to complete. (Basically, get ready to commit yourself to hours of multiplayer.)
If you decide to play
Galaxy at War, this will take several days. Clicking on each section of the map will bring up three available missions. Each mission has a different completion length. 5 hours is the longest one, but provides the most amount of readiness; while 1 hours is the shortest one with the least amount.
As I haven't played
Infiltrator, I can not give any insight as to how that works.
Readiness goes down within several hours on Galaxy at War and within a day of no play on Multiplayer. It is best to check on your readiness on Galaxy at War as often as possible until you've gotten the trophy.
On one last note, you
must have the online pass activated for Galaxy at War and Infiltrator. Without the online pass, the data from the game and app will not sync to your account.
The trophy should pop after syncing to your account to the game. Just loading the menu screen to the game should activate it.
Edit: Galaxy at War can now be found at
http://n7hq.masseffect.com.