Assassin-Templar War

The Assassin–Templar War is a covert war waged between the Assassin Brotherhood and the Templar Order, spanning across most of the known human history.

History
The origin of the conflict is believed to stem from the killing of Abel by his brother Cain, to obtain his brother's Apple of Eden. However, more plausible explanations for the start of the war can be found in the aftermath of the Human-Isu War. The conflict was largely fought through proxy soldiers, by the manipulation of governments and organisations in order to achieve each faction's aims.

It was rare for the conflict to ever become particularly conspicuous, although there were occasions, such as the Third Crusade, where the Assassins and Templars openly fought alongside those they were manipulating. Another example was during the Golden Age of Piracy, where many Assassins attempted to apprehend the Sage Bartholomew Roberts from a Templar convoy, ending in a giant battle in the streets of Havana.

After the Toba catastrophe, the surviving human leaders came into possession of several Pieces of Eden, and debated on how to best use them for humanity's benefit. They were aware of their former slavers interfering with their evolution, and sought to lead humanity on their destined path by any means necessary. In order to achieve this, they utilized the Pieces of Eden as tools, but were distrustful of any who attempted to make peace with the First Civilization.

However, others wanted to give humanity complete freedom, and envisioned a world where all beings could live according to their own will. As such, the maxim "Nothing is true, everything is permitted" became their philosophy, exemplifying the belief that all were free to determine their own path. They also believed that the misuse of the Pieces of Eden to control others was against all they had worked and suffered for, as it would enslave humanity once more.

Throughout the conflict's long history, a number of different powers became involved in it, such as the fledgling United States, the early Soviet Union, the Sikh, Ottoman, French and Holy Roman Empires, aligning themselves with the Assassins, while the Papacy controlled by the House of Borgia, the Russian, Byzantine, and British Empires, modern United States, and Nazi Germany, supported the Templars. These alliances were rarely permanent, however, and often changed along with the leadership of a particular group.

By the 20th century, the conflict had largely removed itself from the public view, with the Templars operating mainly through their front company, Abstergo Industries, while the Assassins struggled to survive on the fringes of society.

The length and devastation of the war had a significant effect on the plans of the Capitoline Triad to avert the Second Disaster. In the Grand Temple in 2012, Juno commented to Desmond Miles that the two factions had wasted centuries by squabbling over Isu artifacts; time which could have been spent on locating the Temple and continuing the work meant to save the world from the solar flare.

Assassins and Templars
Historically, the Assassins and Templars were not above working together towards a common purpose. The first example of such an alliance was with the Levantine Assassin Altaïr Ibn-La'Ahad and the English Templar Maria Thorpe, who worked together to bring down Armand Bouchart, although their motives were initially vastly different.

During a Maroon rebellion in Port-au-Prince, the Assassin Adéwalé was led to helping the brothel owner and Templar ally Bastienne Josèphe defeat the murderous and merciless Marquis de Fayet, who was an infamous slave trader that had ordered a French ship to destroy an approaching slave delivery ship during the rebellion. When Adéwalé decided that justice would be served, he battled overseers and French guards, all dead, and killed de Fayet with a branding iron and his machete. He left later on, leaving the Precursor box that Bastienne sought in her hands. They even had a son later on, and Adéwalé's grandson Eseosa became an influential part of the final Maroon rebellion, the Haitian Revolution.

Another notable alliance occurred during the American Revolutionary War. When Benjamin Church turned on the Colonial Rite of the Templar Order, the Grand Master of the Rite, Haytham Kenway, pursued him with the help of his son, the Assassin Connor, whose aim was to recover the supplies stolen by Church, meant for George Washington's forces stationed at Valley Forge. After Church's death, the pair continued to work together, in order to allow the colonies to gain independence from the British Empire. However, when Haytham revealed Washington's intent to attack Connor's village of Kanatahséton for a second time, the Assassin severed ties with both of them.

During the French Revolution, the Assassin Arno Dorian and his adoptive Templar sister Élise de la Serre hunted the Grand Master of an extremist faction within the Templar Order, François-Thomas Germain, for his involvement in the assassination plot of François de la Serre, former Grand Master and father of Élise, who sought to maintain a truce between the Templars and Assassins. However, such truces were short-lived, since the leaders that succeeded those who brokered them, rarely honored the truce. Mirabeau, the Mentor of the French branch of the Assassin Order, was poisoned by Pierre Bellec, who held a fanatical belief of peace between the two factions being impossible.

In 1868, the Assassin Jacob Frye temporarily aligned himself with the Templar Pearl Attaway, against Malcolm Millner and her cousin, the Grand Master of British Rite of the Templar Order, Crawford Starrick. Jacob was unaware of Pearl's true allegiance however, and immediately resolved to assassinate her upon his discovery.

Other factions
Besides working with Templar defectors, the Assassins also caught the attention of other organizations. During the Renaissance period, Mario Auditore led a band of mercenaries during various assignments for the benefit of the Brotherhood, such as the attack on Vieri de' Pazzi in San Gimignano.

In Venice, and later Rome, Bartolomeo d'Alviano led a company of mercenaries allied with the Assassins. Several brothels in Italy were led by Assassins, including Paola, Teodora Contanto and Claudia Auditore da Firenze, operating in Florence, Venice and Rome, respectively. Some of the thief groups were led by Assassins, such as La Volpe and Antonio de Magianis. However, others opted to stand with the Templars, such as the Cento Occhi, in Rome, or some of the pirates of Nassau, such as Benjamin Hornigold, Josiah Burgess, and John Cockram. Another pirate known as Le Chasseur helped the Colonial Brotherhood during the Seven Years' War, but was killed by Shay Cormac before he could be inducted into the Order as a member.

In modern times, other organizations have taken notice of the conflict between the Assassins and Templars, such as the Initiates, a group of unidentified individuals with vast resources and connections, who eventually allied themselves with the Brotherhood. The hacker collective, Erudito, worked to uncover Abstergo Industries' plots to control humanity; one of their notable activities was hacking the Liberation video game developed by Abstergo Entertainment using edited versions of Aveline de Grandpré's genetic memories. While Abstergo planned to omit all references to the Templars and discredit the Assassins, the Erudito hacks allowed the user to see the original footage and learn the truth.

The Templars also came into contact with the Instruments of the First Will, a group of people who wish to grant control over humanity to Juno, a member of the First Civilization who was freed from her imprisonment in the Grand Temple during Desmond Miles' sacrifice. The Master Templar Juhani Otso Berg mentioned using the Instruments to acquire Pieces of Eden, while the other group siphons Templar resources to achieve their own plan. However, the Templars do not consider the Instruments of the First Will to be a threat, and do not prioritize eliminating Juno, either.