Okay, so, this is the timeline page from the wiki:
World History
It's not going to be exact, but it's a good reference guide for canon.
Dating System:
The Holy Britannian Empire uses the A.T.B. (Ascension Throne Britannia) dating system, which starts (year one) in 55 B.C. with the rise of Alwin 1st as the Celtic Super-King of all tribes in Britain as he successfully repulses the Romans from the British isles.
The Chinese Federation uses a system based on the Emperor/Empress currently on the throne as part of the larger dynasty. The Federation has had, more or less, an unbroken line of dynastic succession from 127 B.C.
The Europa United uses the
French Republic Calendar, which yes, was an actual thing. Year one for that calendar is the storming of the Bastille. It uses ten-day weeks and twelve months to a year. There were only ten hours to a day, and... you know what? I'm not talking about this thing. It's proof that the Enlightenment actually could go too far.
All this means that the dates are as follows, according to Year 1 of this quest:
Europa United: Year 223 of the Revolutionary Calendar
Holy Britannian Calendar: Year 2012
Chinese Federation: Year 2084, Tianzi 7
OTL Year: 1957 A.D.
So, the World of CG makes a big deal about Charles being the 98th Emperor, which is pretty obviously bullshit unless they've had a different Emperor/Empress every two/three years. So why do they say this?
Well, after Queen Elizabeth III (Elizabeth I had a son in this timeline) nominates her lover Ricardo von Britannia as her successor upon her death, Ricardo kind of...
rewrites history a little bit for some extra glory. He basically amalgamated all of the various English dynasties into a single line of inheritance and numbered them, with Alwin I the Celtic Super-King of all tribes as the origin of the throne itself, which explains the new dating system as well.
The Great War:
CC has a series of flashbacks in late S2 that reveal her running through a battlefield:
...which is essentially all we know. Given the other pics show soldiers in traditionally European uniforms common to the late nineteenth and early twentieth centuries, we can surmise that this is likely an analogue for WW1, however... the conflict documented in canon with Lelough forming the U.F.N. and everything? That's supposed to be WW2. Hence why I've been referring to the
singular (as of yet) World War as the Great War up until now.
AU to this Quest, not Code Geass Canon:
Basically, after Napoleon bit it, his empire reorganized itself into a proto-EU along republican ideologies. Spain, having had a
really bad time under Napoleon's conquests (this war gave us the phrase 'Guerrilla Fighter' seriously), decided that it was going to politically rebound (bloodily) as per the OTL mostly back to a monarchy. The rest of Europe, tired of fighting massive wars and trying to stabilize from Napoleon's death and the subsequent power vacuum, didn't want to argue. Spain remained a
mostly stable monarchy, though with a constitution to make the budding EU powers less nervous, until the Great War of the CG timeline.
Monarchist that it was (if a constitutional one), Spain allied itself with Portugal and Russia in an attempt to counterbalance the EU. Britannia, the elder brother of all monarchists, backed all three of them to the hilt and had this crazy plan (which, in my notes I refer to as the 'World Vice') to force the EU to fight a war on two fronts by supporting Portugal/Spain attacking across the pyrenees mountains while Russia attacked from the East.
It went... badly. More on that later, if you get involved with the Euro-Britannians.
Long story short, Spain got invaded after a very long and bloody conflict. Cities were burned, atrocities were committed, the EU doesn't like to talk about the war crimes they committed here, but Spain was subjugated. Portugal took one look at that and surrendered with a few conditions... one of which was that they could declare more or less permanent neutrality and not be forced to join the EU, but in exchange disband most of their standing army and get rid of a lot of their weapons.
Spain, to this day, still hates the EU, but doesn't have anywhere near the kind of military it would need to throw them out, given the large EU military bases still in the country today.
Portugal is as neutral as you can possibly be... while still standing firmly with the Britannians.
Now, there
are reasons for all of this, and they relate to the fact that Britannia reconquered a lot of Spanish possessions in South America and the Portuguese royal family
married into the Britannian one as part of the treaty to semi-peacefully absorb Brazil. ('Or else we'll just take it' was strongly implied by the Britannian Emperor at the time.) The Britannian empire, seeing the value in having European allies, refunded some wealth and land to the nobility and royalty of the two countries and their subsequently intertwined economies necessitated close political ties.
