Conflict between Ascalonian and Modniir Centaurs in Shiverpeaks, How did it happened?

TIL that there are actually 3 different tribes of centaurs in core Tyria, and Modniir was the head of the alliance, pushing for a war against human for a blood feud dated back in GW1 era. According to various accounts, the Modniir tribe was nearly wiped out during the conflict against Ascalonians, who were on a mission northward Shiverpeak Mountains in the chapter Eyes of the North. Having never played GW1 and found very limited resources on the detail of this conflict on the internet, would some one fill in your knowledge :) ?

There's not much to it, alas. All we know for sure is that the Modniir were nearly wiped out by humans AND norn at some point before GW2. A lot of folks infer that means the period in Eye of the North when our characters, the Ebon Vanguard, and the norn were all romping around the Far Shiverpeaks together, since that's the only time we know of when the humans had any significant presence in Modniir territory. However, there was never actually a plot point that involved them, only a single side quest where they launched an attack against the Vanguard. Other than that, they were just one of a dozen wilderness hazards that we dealt with as we came across them.

Thank you so much :D It is kind of disappointing though seeing that the developers did not expand on this part further.