protoss serial xenocide(aka; just exactly what have the protoss been up to)

This is irking me significantly. The protoss are a warlike race with a warrior culture. At least 2 important characters, Fenix and Artanis have fought battles together before the events of starcraft.
The koprulu sector had inhabitants before the terrans got there, yet none survived to meet the terrans, is the hand of the protoss visible in this?
Yet on the other hand, the Protoss were horrified by the collosus and said they would never interfere in lesser races. Yet Artanis has fought in wars alongside fenix as well, and he was born after the Kalathi intercession, not to mention the fact that he only thinks of his past battles as glorious.

Have the protoss defeated and exterminated a species that they deemed equal to themselves? Where are the remnants of this species? How advanced were they?

 

The protoss colonies probably covered a much larger area of space than the Koprulu Sector. The terrans don't have access to warp gates or anything like that to help them "cheat" their way through the stars.

The protoss "Dae'Uhl" prevents them from interfering with "lesser" species. The kalathi were certainly a lesser species, given how easily the protoss steamrolled them. However, they got scared of what they had done.

Shadow Hunters pointed out the protoss did engage in conflicts with other species, winning them, but this was before the Kalath Intercession.

 

I am kinda tired and drunk on tiredness, so my posts may seem a bit jumbled.

My main points were:
1. Artanis is (very likely) younger than the Dae'Uhl. (the kalath intercession took place a few centuries ago, Artanis is 262 years old at the time of brood war).
2. The koprulu sector used to be inhabited, but something killed everything
3. the protoss would not intervene with lesser races, so the enemies after the kalath intercession would have to be equal or greater


I found an interesting bit, one of the races Artanis and Fenix fought were the Tagal, where the protoss won a battle while outnumbered 30:1.

and another

Artanis and Fenix fought among hundreds of worlds.
Which means hundreds of world were populated at one point.
Yet still, the Terran only met the Protoss and Zerg. And the first one was because they refused to interact with a lesser race and the second one because they hadn't arrived yet.

 

1) The Kalalth Intercession took place after the Rogue Strife (which was 1000 years ago). I don't believe we're given a more specific time period for the Kalath Intercession though.
2) I think many of the ruins are xel'naga ruins. (In which case, the xel'naga weren't killed off [until the zerg did it] but simply left once they were done with a planet.)
a) Although there may be vague hints to the contrary. I shouldn't assume that all those non-protoss ruins are xel'naga, but we don't know about other races that could have left them.
3) Yes, I believe there's actually lots of alien races out there, and some might be quite powerful, but I think the protoss empire covered a far larger territory than the Koprulu Sector, and that the terrans "lucked out" by falling into a patch of space uninhabited by other intelligent species.

And yes, the tagal are out there... although Blizzard wasn't even sure if they'd make them canon in interviews. (They never actually got mentioned in the lore; they appeared in a cut mission.)