X Chronology
20XX period? [sic]
Dr. Light develops X
After sealing X, Dr. Light dies
21XX period
Dr. Cain discovers X, develops Repliroids on the basis of X
Dr. Cain organizes the Irregular Hunters, makes Sigma their leader
X is assigned to the 17th Squadron
Title: RMX
The Sigma’s Rebellion Incident
(half a year)
X takes the position of Captain of the 17th Squadron
Title: X2
The Counter-Hunter Incident
Title: Cyber Mission
The Mother Computer Hacking Incident
Title: X3
The Doctor Doppler Incident
The existence of Sigma Virus becomes known
(interval)
The founding of Repliforce
Title: Soul Eraser
The Soul Eraser Incident
Title: X4
The Repliforce War
(several months)
Signas, Alia, and Douglas become X and Zero’s support staff
Title: X5
The Falling Colony Incident
All areas of the Earth are devastated from the influence of Sigma Virus
(three weeks)
Irregular Hunters diminish in number
The entire organization, including the 17th Elite Squadron and the 0th Special Squadron, is dismantled and reorganized
Title: X6
The Nightmare Virus Incident
(interval)
X, harboring doubts about a military solution, retires from action
Irregular Hunters weakened
Title: X7
The vigilante group Red Alert begins action
The Red Alert Incident
Axl joins the Irregular Hunters
X returns to action
Zero Chronology
21XX period
Sigma finds Zero running amok, subdues him. He is assigned to the 17th Squadron, where he can also be supervised
Title: RMX
The Sigma’s Rebellion Incident
Zero wrecked
(half year)
Zero in irreparable state
Title: X2
The Counter-Hunter Incident
Zero revives
(interval)
Zero takes the position of Captain of the 0th Special Squadron
Title: Cyber Mission
The Mother Computer Hacking Incident
Title: X3
The Doctor Doppler Incident
The existence of Sigma Virus becomes known
(interval)
The founding of Repliforce
Title: Soul Eraser
The Soul Eraser Incident
Iris receives operator training as an Irregular Hunter
Title: X4
The Repliforce War
Iris dies
(several months)
Signas, Alia, and Douglas become X and Zero’s support staff
Title: X5
The Falling Colony Incident
All areas of the Earth are devastated from the influence of Sigma Virus
Upon resolution of the incident, Zero is MIA
(three weeks)
Irregular Hunters diminish in number
The entire organization, including the 17th Elite Squadron and the 0th Special Squadron, is dismantled and reorganized
Title: X6
The Nightmare Virus Incident
Zero revives
(interval)
Zero voluntarily seals himself for 100 years? [sic]
Irregular Hunters weakened
Title: X7
The vigilante group Red Alert begins action
The Red Alert Incident
Axl joins the Irregular Hunters
Translator’s Random Notes: The X6 guide does list X as former Captain of the 17th, so the reorganization must have taken place already. But nowhere have I found details on how it was reorganized, so I can’t confirm the part about Signas having sole responsibility. As for humans not learning from their previous mistakes, I think that is a basic theme of the series.^^; But Repliroids seem no better.
If X retired and Zero locked himself up after X6, then I can see how the Hunters would be weakened, with their two best recruiting poster boys gone, and something like Red Alert could spring up in the vacuum. I don’t think they would both walk out at the same time, though.
As for Hunter rank, I think it has less to do with their position in the organization and more to do with the type of situation they’re appropriate for. If it’s one Metool with a screw loose, you wouldn’t send an S-class. On the other hand, you wouldn’t (normally^_^) send a B-class to take down Sigma.
(Deleted and reposted for format trouble)