United Republic of Europia

The Euro Universe (ユーロ・ユニバース, Yūro Yunibāsu) is one of the three major superpowers in the world in which Code Geass takes place. Its creation is estimated to be in the 19th century a.t.b., around the time of the Industrial Revolution, following Napoleon Bonaparte's successful invasion and occupation of the British Isles. This caused the royal family to be exiled to their American colonies, which had recently been neutralized following Washington's Rebellion, and ultimately brought about the foundation of Britannia. However, Napoleon suffered a major defeat at Waterloo in 1870 a.t.b. (1815 A.D.), destroying his hopes of invading and subjugating Russia. Russia would eventually join the E.U. anyway, though the reasons for this are unknown as events between 1870 and 2010 a.t.b. are never explicitly explained. It may be that events similar to the World Wars of our timeline occurred (evidence of trench warfare and WWI-era tanks can be seen in flashbacks concerning C.C.), and some kind of bond was formed between Russia and the rest of Europe. Europe also seems to have undergone a Scramble for Africa similar to our own, as the entirety of Africa is part of the Euro Universe(most likely colonial as the series seems to have pitted the 3 super powers in the same scramble for colonies that occured in the late 1800's, these areas probably are of little relevance)

Though geographically the largest of the three superpowers at the beginning of the series, the Euro Universe (often abbreviated to E.U., a clear reference to the real world European Union) receives little attention in the show. In 2018, Schneizel led Britannian forces against the E.U. and successfully conquered almost half of its territory in an unknown amount of Areas. Following this defeat, some members of the E.U. joined the United Federation of Nations, and Britannian forces were pulled away from the fronts in the E.U. as the Emperor of Britannia no longer considered the country a threat. By the time Lelouch ascended to the throne, all members of the E.U. were neutral or had ratified the United Federation of Nations' charter.

Light Novels
The EU is referred to as the 'European Ultra-Union' in the 'Stage -0- Entrance' Light Novel (p. 27).

Geography
In the first season, maps showed the Euro Universe controls not only Europe (including the regions of Russia officially considered part of Asia), but also all of Africa and parts of the Middle East. After Britannian forces pulled out of the E.U., they had lost much of North and West Africa, southern Africa, France, the Low Countries, the Iberian Peninsula, and Russia. While many E.U. member-states ratified the UFN's charter, the British Isles, Germany, Denmark, Scandinavia (and the Kola Peninsula), and parts of Central Africa and the Middle East remained independent.The fact that all of Africa was part of the E.U. would seem unlikely, but it may be that those territories were colonies of European powers.

Government
The Euro Universe is probably the most democratic of the three superpowers, but is also very divided. Beyond this, little is known about the E.U.'s government, though it is likely some kind of council with representatives from each member-state present. This council has, in some sources, been referred to as the Central Hemicycle. Given that the E.U. was founded by Napoleon, it could be that it's capital city is Paris. Then again, since the Euro Universe is based on the real-life European Union, it could be that it's capital is Strasbourg. It is even possible that the Euro Universe doesn't have a single capital city.

Military
The Euro Universe's collective military forces are divided into individual national forces referred to as "state armies," though the exact nature of these armed forces is not clear. From what is shown, the only Knightmare Frame that the E.U. uses is the Panzer-Hummel, which appears to be somewhere between the technological level of the Chinese Gun-Ru and standard Britannian knightmares, though they are shown to be quite effective against Sutherlands and Gloucesters at range. These E.U. ground forces only make one significant appearance, in R2 Stage 03, Imprisoned in Campus. The E.U. pilots displayed enormous courage, attacking Suzaku with little hesitation in spite of his reputation as "Britannia's White Death."

Euro Universe officers and personnel are shown to wear gray uniforms with a gold diamond logo, which may be an emblem of the E.U. But, since the E.U. Armed Forces is actually several armies band together, it could be that the golden diamond logo is the logo of a "state army" rather than the emblem of the E.U. Military as a whole. The E.U. is described as having once enforced a blockade upon Britannia in cooperation with the Chinese Federation during the "Indochina Incident," which implies significant naval capability. However, the same source indicates that Britannian vessels were shut out of the waters of developing countries, which may imply diplomatic efforts rather than military might.

The existance of Akito Hyuga suggests that the E.U. may have employed Japanese exiles as soldiers (possibly as conscripts or volunteers). They wore noticeably different uniforms to those shown in R2. It is likely that these Japanese soldiers are part of some kind of E.U. "Foreign Legion", akin to the real life French Foreign Legion.

Overall
Britannia once took the E.U. seriously as an opponent, at least before the establishment of the UFN; Cornelia, in the ninth episode of the first season, Refrain, wanted to return to the battlefield after she heard of an E.U. advance on the El-Alamein Front (presumably in Egypt), and Odysseus at another time warned against attacking the Chinese Federation while still being at war with the E.U.. The battle portrayed in Imprisoned in Campus showed that the E.U.'s military capability is a broad match for Britannia's, though the reason for its defeat seems to be as a result of Schneizel's outside-the-box thinking, conducting negotiations with individual members of the E.U. rather than with the union as a whole, and persuading them to surrender willingly rather than being destroyed. This fits with Schneizel's oft-stated belief that conquered nations should be treated with dignity and allowed some hope.

Trivia

 * The borders of many, if not all, member-states of the E.U. are identical to those of our world, which is pretty interesting since many of the modern-day European borders were drawn as a result of events that probably didn't occur such as WWII (ie. Germany's Eastern border with Poland at the Oder-Neisse Line), and the collapse of the USSR (ie. existence of independent Ukraine).
 * Geographically speaking, the E.U. is quite similar to Eurasia from George Orwell's Nineteen Eighty-Four; this country was locked in a perpetual war with Oceania (which is similar to Britannia) and Eastasia (most similar to the Chinese Federation) and would occasionally ally with one or the other for its own benefit. Occasionally, Eurasia would take over northern Africa and parts of the Middle East, much like the E.U. in Code Geass, before once more losing them to either Oceania or Eastasia. The major difference is that Eurasia was created by the Soviet Union and was a totalitarian state much like Oceania; in fact, Britannia is more comparable to Oceania than the E.U. or Chinese Federation is to Eurasia or Eastasia in that their political setup is much more similar.
 * The fact that Britain remains separate from both the UFN and Britannia (following France's capitulation) shows that Britain retained its independence after being conquered by Napoleon, most like as an ally or client state. If Napoleon followed his usual policy by that point, Britain may have recieved a new monarchy, the most likely candidate being a blood relation of Elizabeth III (willing or otherwise), a relative of Napoleon himself, or one of his Marshals. It is interesting to note that Britain refuses the UFN alongside Germany and the Scandinavian countries, suggesting some connection with them.
 * On the other hand, considering the anti-monarchist idealogy of the EU, it is possible that Napoleon would have simply removed the monarchy completely and established a new executive branch of the government, if not expand the power and duties of the Prime Minister to encompass them (similar to what eventually happened in OTL). Another possibility would be his reestablishing the Commonwealth, alongside a new Council of State or a Lord Protector to act as the head of state. Overall, there are many possibilities.