One of the first iterations of the Brotherhood was founded in Krete by the Hidden Ones Marcus Junius Brutus in 44 BCE when he took refuge on the island after the Assassination of Julius Caesar. With his recruits, Brutus tried to eliminate the tyrants of the island.
In 1511, the Greek Assassins in Athens were having problems with retaining the trust of the people since the city came under Ottoman rule. Receiving aid from the Ottoman Brotherhood, they convinced the people that they were an independent organization, not working for any nation. Together, the two Brotherhoods also prevented the Ottoman soldiers from looting the Greek people, who acted against the orders of the Sultan.
That same year, the Rhodian Master Assassin Castor was captured by the Knights Hospitalier. Ottoman and Greek Assassins sent by Ezio Auditore found that he had been murdered, and in retaliation, they burnt down the Hospitalier Compound.