Origin

In the year 2246, the Followers of the Apocalypse sent a group to the Grand Canyon to study the region's tribal languages. The group included the Follower Edward Sallow, the Follower physician Bill Calhoun, and the Mormon missionary Joshua Graham, with the last mentioned being a specialist in tribal dialects. Not long into their travels, the group was captured by the Blackfoot tribe and held for ransom.

At the time, the tribe warred against seven other tribes and suffered from a lack of skill in warfare. Sallow noticed the Blackfoots' martial ineptitude and feared that their more numerous enemies would soon overwhelm them. Unwilling to leave his and his comrades' fate up to chance, and against his companions' wishes, Sallow instructed his captors in the arts of war, granting them knowledge in gun maintenance, small unit tactics, explosives, and military strategy, drawing largely on what he had read about the military tactics of ancient Roman legions. Under his guidance, the Blackfoots not only defeated but subjugated the neighboring tribes and came to respect Sallow, following him as their leader. Sallow granted himself the name Caesar and began reorganizing the tribals he commanded into the Legion.

Caesar established warfare policies in the Legion based on the Roman concepts of "divide and conquer" and "total war." The Legion defeated the region's seven tribes from weakest to strongest and completely dominated each tribes' land and people, subsuming them into his growing army. Those who surrendered were conscripted and the remainder were either enslaved or killed. Caesar saw the tribes "playing at war," and tribals viewed his tactics as foreign, accustomed only to minor skirmishes and raids that never escalated into major conflicts.

Under the combined leadership of Caesar and Graham, the latter of whom had been declared the "Malpais Legate," the newly-formed Legion led numerous campaigns against other tribes, forming a fanatically loyal army of assimilated warriors. In the early days of the Legion, the powerful Twisted Hairs tribe of Arizona would aid the Legion as scouts. However, the Legion would eventually break the alliance and conquer the Twisted Hairs as they had with many other tribes, erasing their tribal identity and crucifying those who resisted along Interstate 40.