The latest episode of The Mandalorian, "Chapter 14: The Tragedy," dove deep into the history of the Mandalorians in more ways than one. Din Djarin encountered Boba Fett, who came to claim his old armor. The two fight at first but soon had to team-up against Moff Gideon's Imperial remnant. Eventually, Boba Fett proved his claim to the armor by showing Din Djarin the chain code in his armor. The code confirmed Boba as the son of the foundling Jango Fett while also bringing another important Mandalorian into the new canon. Boba Fett also says that his father fought in the Mandalorian Civil Wars. While the new Star Wars canon hasn't explored this part of Mandalore's history, it was a significant turning point in the Star Wars Legends canon.
The Mandalorian Civil Wars took place before the events of The Phantom Menace. As detailed in the comic book miniseries Jango Fett -- Open Seasons, the wars began after Jango Fett's adoptive father, Jaster Mereel, became Mand'alor, leader of the Mandalorian clans. As Mand'alor, Jaster tried to enact the Supercommando Codex, a code of conduct that would cast the Mandalorians as honorable mercenaries.
Mereel's new code led to the Death Watch splinter group's formation. Death Watch wanted to return the Mandalorians to their old lifestyle as marauders and raiders. War broke out between the Death Watch and Mereel's True Mandalorians faction. The war lasted for a decade.
Early in the war, Mereel rescued Jango Fett from Death Watch during the Battle of Concord Dawn. Since Jango's parents had died, Mereel adopted the child. The conflict continued with Mereel leading to True Mandalorians until the Battle of Korda Six. During that battle, Mereel was betrayed by one of his own and killed.
Jango Fett followed in his adoptive father's footsteps. He became the new Mand'alor and leader of the True Mandalorians. The war continued until the Battle of Galidraan, when Death Watch's deception brought the Jedi into the conflict. Death Watch tricked the Jedi into believing that the True Mandalorians were killing civilians. A group of Jedi led by Dooku arrived on the planet and battled the True Mandalorians. The True Mandalorians killed 11 Jedi, but the Jedi wiped out every True Mandalorian but Jango Fett. This tragedy is why Jango Fett showed such animosity towards the Jedi in Attack of the Clones.
The destruction of the True Mandalorians led to a second civil war between the Death Watch and the reformist New Mandalorians. Under the leadership of staunch pacifist Duchess Satine Kryze, the New Mandalorians eventually won control of Mandalore, installing the duchess as the new Mand'alor. Death Watch would later return, as chronicled in Star Wars: The Clone Wars, inciting another Mandalorian civil war.
Jango Fett went on to live the life of a solitary bounty hunter for a time. After Count Dooku's fall to the dark side and transformation into the Sith Lord called Darth Tyrannus, the former Jedi reached out to Jango Fett with the offer to become the template for the Grand Army of the Republic. Jango accepted the offer, leading to the creation of his clone son Boba Fett. It also led to his encounter with Obi-Wan Kenobi on Kamino and death at the hands of Mace Windu during the First Battle of Geonosis (all seen in Attack of the Clones).
We don't know how much of this is part of the new canon or whether Jango was really ever Manda'alor or just a soldier, but the episode does confirm an important part of Star Wars history.
New The Mandalorian episodes stream on Fridays on Disney+.