The Holy Britannian Empire was the most powerful nation in the world, eventually having control of a third of the world. The homeland is located in Britannia in North America, where Pendragon - the Imperial Capital - is located. When Emperors appears on the battlefield, they are often seen traveling in the Avalon, a mobile command center that later evolved into a flying fortress.
Reign of Charles zi Britannia, the 98th Emperor
Born out of a time of conflict between the royal houses, the family of Charles zi Britannia emerged victorious, resulting in his ascension to the throne as the 98th Emperor.
Charles zi Britannia married many wives in his time, but paid particular attention to Lady Marianne vi Britannia, with whom he shared some of his dark secrets regarding Geass - a supernatural ability that is based in the eyes - as well as some of his true intentions to reshape the world through Geass. By Charles' side was his older brother, who went under the name V.V. and acquired immortality. V.V. gave Charles the Geass ability to change memories in others. C.C., another immortal, gave Marianne the power to possess another body.
Lady Marianne was mysteriously assassinated. This action was mostly ignored by Charles, who in truth intended to find the one responsible. During this time, he sent Marianne's children - Prince Lelouch vi Britannia and Princess Nunnally vi Britannia - to Japan as diplomatic envoys, after they were both physically and psychologically scarred after witnessing Marianne's death.
Acquisition of Japan
Despite Britannia's claim at a diplomatic resolution, they invaded Japan, using their new weapon, the Knightmare - a mobile mech suit that proved faster and more agile than any tank. Japan was quickly overwhelmed, renamed Area 11 and its people called "Elevens." During the attack, it was believed that Lelouch and Nunnally perished.
By 2017 a.t.b., about seven years following the invasion, one of Charles' sons, Clovis la Britannia, became the Viceroy over Area 11. Area 11 became a hotspot for terrorist activity, where a group of Elevens attempted to overthrow the regime. However, in a strange turn of events, the terrorists won a battle against Britannian forces. Following the battle, Clovis was assassinated. Princess Cornelia li Britannia and Princess Euphemia li Britannia went to Area 11 with the intention of restoring order and finding Clovis' killer, who had become known by the public as "Zero."
As the situation escalated, this "Zero" formed a group known as the Order of Black Knights from what used to be a small band of rebels. They were secretly given Knightmares from Japanese benefactors that received them from allies in India. In a major battle between Britannia, the Black Knights, and remnants of the Japanese Liberation Front in what would be known as the "Battle of Narita," Britannia suffered heavy losses as Zero ordered the collapse of a mountain, resulting in multiple Britannian deaths and the deaths of civilians in the village below. This battle saw the apparent loss of Jeremiah Gottwald, whose Knightmare was destroyed by Kallen Kozuki.
Later, in a strange turn of events, a group of Japanese officials who fled during the invasion returned from China - who denied affiliation. Suzaku Kururugi, major and knight to Princess Euphemia, entered the battle utilizing the upgraded Lancelot Knightmare Frame. Suzaku defeated a great number of them, but was defeated due to the unexpected power drain from its new float system. However, Zero entered the battle, in a public declaration that these Japanese were not affiliated with him. Zero and Suzaku defeated them, and Zero escaped once more.
The Special Zone
Without permission from command or the viceroy - Princess Cornelia - sub-viceroy Princess Euphemia announced the creation of the Specially Administrative Zone of Japan, where Elevens would be allowed to speak and call themselves Japanese. She publicly asked that Zero join her in leading the Special Zone.
In a public ceremony commemorating the Zone, Euphemia and Zero met in privacy. It was not known by the public, but Euphemia had some how changed from the meeting. She emerged, ordering the deaths of all Japanese in the stadium.
Following the mass execution of countless Elevens, the Black Knights entered the battle under Zero's command. Zero, personally, shot Euphemia during the battle. Princess Euphemia later died aboard the flying mobile command center, the Avalon. Because of this act, Zero gained even more support from the general public.
The Battle of Tokyo
Directly following the massacre, the Black Knights - as well as supporters from the surrounding towns - marched on Tokyo, the headquarters of the Britannian garrison in Area 11. Princess Cornelia prepared to meet his forces, but was unaware that he had secretly arranged for Tokyo to release its support structure - this support structure was intended to protect the city from natural disasters, but now served as a grave for many Britannian soldiers.
For the majority of the battle, the Black Knights were winning, despite the odds. However, mysteriously, their commander Zero disappeared. Without their leader, the Black Knights were overwhelmed and defeated. Zero retreated to parts unknown, and was thought dead.
In reality, Major Suzaku Kururugi captured Zero. Zero was brought before Emperor Charles zi Britannia. Zero was unmasked and revealed to be the thought-dead 11th Prince, Lelouch vi Britannia. Lelouch's mind was wiped of his memory of being Zero. As a reward for his capture, Suzaku Kururugi was made a Knight of the Round, given the title "Knight of Seven." Following the Black Knight's swift defeat, that era of conflict would become known as "the Black Rebellion."
After this, there was a period of unrest in central Europe between Britannians and some European loyalists, who hid behind their soldiers so as to protect themselves from reprisal.
One Year Later
Britannia gained a new hold over Area 11, and earned itself a new viceroy - Duke Calares, who took the position after Princess Cornelia left in search of an answer as to why her sister committed genocide. Under Calares, many Black Knights and Japanese loyalists were publicly executed, and Area 11 was subjugated worse than before. Britannia had also become talks of alliance with the Chinese Federation.
This period without conflict would not last, however. Zero returned, the former prince regaining his memories after a year, killing the viceroy during his escape. He then began to rebuild the Black Knights, once more intending to bring down the entire Holy Britannian Empire. To that end, the Emperor's elite - the Knights of the Round - took a more active role in Area 11, particularly the Knight of Seven, Suzaku Kururugi.
During this time, a new viceroy was put in charge of Area 11: Lelouch / Zero's sister, Princess Nunnally vi Britannia.
Prince Schneizel el Britannia took an active part in allying the Chinese Federation and Britannia. To that end, he intended to marry the 1st Prince - Prince Odysseus - to the Chinese empress, Tianzi, in order to officially unite the two nations. At the wedding banquet, the Holy Britannian Empire and the Chinese Federation were surprised by the arrival of the Order of Black Knights, with Zero at the lead - who, because they were in China, were technically on neutral territory. Zero challenged Prince Schneizel to a game of chess, but this was ended in a stalemate.
During the wedding ceremony, Zero attempted to kidnap the princess. Because of the location of the battle, Britannia was forbidden to take an active role in the fight. Zero used the battle to his political advantage, manipulating the High Eunuchs - the ruling class in China - into revealing their intentions to the world, resulting in open rebellion throughout China. In the end, the High Eunuchs were killed, and Britannia lost China as its ally, who joined with Zero. Because of this, the Black Knights, the Chinese Federation, and other allies in disgruntled Areas banded together, creating the UFN - the United Federation of Nations.
Not long afterward, the Geass Order - a small group operating within Britannia - sent an assassin, Jeremiah Gottwald, to kill Zero. However, in a surprising turn of events, Gottwald turned against Britannia and sided with Zero, once he realized that Zero was the former 11th Prince, Lelouch vi Britannia. Gottwald and Lelouch then went on the offensive, using a small strike team to cripple the Geass Order. During the battle, Director V.V. of the Geass Order was wounded, and his immortality was stolen from him by Emperor Charles zi Britannia, making the emperor immortal.
Second Battle of Tokyo and Death of Charles zi Britannia
The Black Knights engaged in a second Battle of Tokyo, with the intention of capturing the viceroy, Nunnally vi Britannia. For the majority of the fight, the Black Knights appeared victorious. The Knight of Ten, Luciano Bradley - the "Vampire of Britannia" - was killed in combat by Kallen Kozuki. Knight of Seven, Suzaku Kururugi, appeared to be at near defeat. However, at the last moment, he fired the ultimate weapon at Britannia's disposal - the FLEIJA, a weapon of mass destruction that almost completely destroyed the Tokyo Settlement, resulting in countless military and civilian casualties, including the apparent death of Nunnally vi Britannia. Britannia and the Black Knights temporarily agreed to a cease fire as they helped civilians in the aftermath.
The 2nd Prince, Schneizel el Britannia, also met with the leaders of the Black Knights. He revealed Zero's royal background, resulting in the Black Knights turning on their leader. Lelouch, however, escaped in his Knightmare frame.
No longer hiding his identity, Lelouch went on the offensive, going after his father - Charles zi Britannia. A small band of Britannians even stepped aside for Lelouch, recognizing him as prince. Lelouch then fought and killed Charles zi Britannia; during this battle, Suzaku Kururugi oddly sided with Lelouch.
After one month, people did not know where the Emperor was. However, during a set public broadcast at the Britannian royal palace, the Pendragon, Lelouch vi Britannia stepped forward, claiming his right to the throne. The 1st Princess, Guinevere su Britannia, ordered Lelouch's death. However, Suzaku Kururugi stopped those soldiers. Lelouch named Suzaku the Knight of Zero, putting him above all other Knights of the Round.
Lelouch used the power of Geass to order loyalty to all those in the room, who chanted his name.
Reign of Lelouch vi Britannia
Prince Schneizel contested the rule of Lelouch vi Britannia, resulting in two split factions within Britannia: The main Holy Britannian Empire - allied with Emperor Lelouch vi Britannia - and the splinter Britannia faction led by Prince Schneizel - allied with the Black Knights. The Knights of the Round, other than the new Knight of Zero, allied with with Prince Schneizel. With a small group of soldiers, the Knights of the Round attacked Pendragon. However, they were swiftly defeated by Knight of Zero, Suzaku Kururugi.
The Holy Britannian Empire is a monarchy led by the Britannian Royal Family. Ruling families were known to feud between the Britannian houses.
The sovereign leader is the Emperor or Empress of Britannia. The title is passed on along the bloodline. While typically the firstborn of the current Emperor / Empress will become the next in line, it is up to the discretion of the Emperor to decree who is next in line. The Emperor often has many wives.
The middle initial of each Prince / Princess signifies which side of the family / which wife they were born to. For example: Lelouch vi Britannia was born to Marianne vi Britannia; Euphemia li Britannia, on the other hand, had a different mother.
Princes and Princesses often serve as military commanders, rulers of Areas (annexed countries conquered by Britannia). Often, they have a knight who will protect them on and off the battlefield. These knights also act as advisers.
Britannia has within it a series of groups that each serve very specific purposes.
Camelot is a very small Research and Development group in Britannia. This group primarily answers to Prince Schneizel el Britannia and is headed by lead scientist, Earl Lloyd Asplund. Working with Camelot is Lloyd's assistant, Cecile Croomy, and their "Devicer," Suzaku Kururugi. While their standing within the command structure is technically low, they carry a great deal of weight because they report to Prince Schneizel, and therefore they often ignore military commanders in pursuit of their goals. Their headquarters usually varies depending on where their creations will be utilized, but their primary HQ is aboard the Britannian mobile command center, the Avalon, which they personally a hand in enhancing.
Their primary purpose is the creation and application of new technology. This usually begins with their enhancements of Knightmare mech combat units, and the technology therein is later applied to other aspects of the Britannian military.
The origins of the Geass Order are mysterious. It is unknown whether they originated with Britannia. When they were disbanded, they were under the direct control of Emperor Charles zi Britannia.
The existence of the Geass Order was kept secret, as was the existence of Geass itself. It was only known to a select few high-ranking people within Britannia. For some time, it was under the command of C.C., and immortal Geass user, who was allied with the royal family. C.C. abandoned the Order when it became clear that she was in danger of another immortal, V.V., who had his own aspirations. V.V. became the Director of the Geass Order after she left.
The Geass Order was responsible for many experiments involving Geass, which would include Rolo - a child assassin - and Jeremiah Gottwald, a cyborg who was given a Geass Canceler, which allowed him to cancel the effects of Geass on other people as well as himself.
Their goal was the destruction of the conceptual sub-conscious, removing free will and eventually making the entire world one.
In the end, the Geass Order was destroyed by Lelouch vi Britannia and his Black Knights.
Knights of the Round
Being a Knight of the Round is a great honor in Britannia. A Knight of the Round is not bound by the standard Britannian command; they answer only to the Emperor of Britannia. Each Knight is given a rank of one through twelve. This number does not signify rank, as none of them have command over one another - the exception being the Knight of One, who is considered the leader of the Knights and recognized as the strongest. During missions, a Knight of the Round will often take direct command over the battle.
After the ascension of Emperor Lelouch vi Britannia, the 99th Emperor, a new title was created: the Knight of Zero, which was bestowed to Suzaku Kururugi, Lelouch's personal Knight. During the Britannian Schism between those loyal to Emperor Lelouch and those loyal to Prince Schneizel el Britannia, who the majority of the Knights recognized as the rightful ruler, the Knight of Zero single handedly killed multiple Knights of the Round, including the Knight of One - officially making the Knight of Zero, Suzaku Kururugi, the strongest of the Knights.