Ana's mgmt dossier - Thargoids and war
The alien race which humans call "Thargoids" has been around for several millions of years, longer than any other race known to humankind.Already long before humans climbed down from trees, the Thargoids "seeded" planets and moons close to what later became the human "bubble" with so-called Barnacles, organo-mechanical "plants" which harvest materials underground and produce Meta Alloy, a commodity highly priced by humans.
When humanity started to spread from Sol, they encountered these Barnacles and plundered them for the Meta Alloys, thereby damaging and partly also "killing" them.
The Thargoids did not like that and started to attacked human ships encountered in the systems the Thargoids probably count as "theirs" (due to the presence of Barnacles).
Humans fought back; this escalated in the first Thargoid war, ended by humanity developing the "Mycoid" virus, which was deployed by John Jameson in 3151 (be sure to visit the Jameson crash site in HIP 12099 1 B!) and drove them back for about 200 years. This is by and large considered as humanity's first attempt at genocide towards the Thargoids.
A few years ago (and now immune to the Mycoid), they returned to again try to claim back their systems and installations; conflict arose again and has been going on ever since.
The latest chapter started when Caleb Wycherly (aka "The Witch", self-styled "Salvation" and responsible for both mass-murdering humans as well as the first Mycoid-based attempt at genocide - yes, he is that old) developed another "super-weapon", the Proteus Wave, which gloriously backfired.
But it succeeded in making the Thargoids angry enough (after being extremely defensive and reserved for hundreds of years) to unleash the invasion from 8 maelstroms - what we today call the second Thargoid war, triggered by humanity's second attempt at genocide.
Attempts at communication have been sparse, and have been curtailed by the powers-that-be (e.g. by murdering or abducting scientists who were considered dangerously close to be able to communicate). It seems fighting this war is too profitable for many powers to be allowed to stop.
Therefore, and because of the very negative, aggressive role humanity have played in escalating these conflicts again and again, many commanders object to fighting Thargoids.
Others claim that, no matter the history, humanity must be defended and cannot retreat.
Even others are "Starship Troopers" just wanting to kill some bugs in a "only a dead bug is a good bug" mentality.