In the deep recesses of the 1990s, there was a one season wonder called Space: Above and Beyond. Many of its precepts have aged poorly and were kind of nonsensical at the time, it was a kind of Top Gun meets Full Metal Jacket in space. But I think it was neat.
One of the things that just sort of popped into my brain as I was remarking on the similarity of the side profile of a TIE-Fighter to the Chig main battle carrier was why did the Chigs even have a military in the first place? This a setting with only two and a half known space faring species after all.
Chig culture is only very abstractly sketched out because the series is human centric and the showrunners wanted to try to preserve some of that sense of the unknown rather than humanize their antagonists too early. Makes sense when you recall this shares creative DNA with the X-Files. What we are told though implies that they are fairly harmonious internally. No sign of balkanization or the necessity to have a large standing military to pacify rebellious colony worlds.
Well an answer is kind of staring us in the face and I think its one that, if true, would be kind of novel:
The Chigs militarized in anticipation of a conflict with Earth. Not to invade Earth, but because they believed Earth would preemptively attack when contact was made. For the Chigs, Human settlement on what was a "sacred site" (albeit one they somehow never thought they needed to communicate to Humans) fulfilled the self fulfilling prophecy.
Early contact with the rogue AIs that fled Earth and signals intelligence convinced the Chigs that Humans were going to be a problem that the Chigs needed to be prepared for and eventually, Humans became a problem the Chigs needed to be prepared for. And interestingly enough - and this might be because in the back half of the first season the showrunners were pretty sure they were getting canceled - the Chigs are losing within the first season.
Which is further evidence that, poorly thought out and brutal reaction to Human encroachment in their space aside, the Chigs really didn't have much of a military instinct to begin with. Their technology is very good but the designs they fielded weren't and by the time they realized they needed to do a lot better, one exceptionally nasty prototype fighter wasn't going to change the outcome of the war. A war they technically started but again there's reason to believe they armed in reaction to observing that Humans were entering their interstellar age fielding entire carrier battlegroups despite having every reason to believe they were alone in the universe aside from their own creations who, unlike the Cylons, were not able to lay claim to much in the way of heavy weapons or industry in the divorce.
Of course its entirely possible that given the extreme reaction to Human settlement, the Chigs entered their interstellar age ready for war and fielding entire carrier battlegroups just like their long lost panspermia cousins would, but its a fun theory to think about aliens just chilling in their own corner of the universe, only to start getting really freaked out by upstarts who are militarized seemingly just out of habit and the first impressions of said species being first contact with the first of no less than two artificial slave races and Humans landing on a sacred nature preserve - that apparently a Weyland-Yutani style secretive corporation had reason to know was taboo and didn't bother telling anybody else.
