Ryujin
Legend
Fer giggules, I checked out the show’s fan wiki.
http://orville.wikia.com/wiki/Krill
According to it, The Union has yet to declare war in the Krill, but that “the conflict” has gone on for a few years, and that the nature of the disagreement means it “could last decades”. The wiki doesn’t detail much in the way of ship-to-ship skirmishes, instead noting that the Krill have done raids in installations & colonies over the past year or so.
In a way, the dynamics between the two is less like tahat of the Federation-Klingon interactions and more like the earlier back and forth between the Federation and the Romulans. The Romulans started off nuking Fed colonies, and both sides were still in the earliest stages of gathering intel about each other. Remember, the Feds were surprised to note the resemblance between Romulans and Vulcans.
To me, at least, the Union-Krill fight seems inits earliest stages as well. So, like I said, this episode may mark the first capture of a Union officer.
IIRC the Romulans were supposed to be a stand-in for Communist China and the Klingons were the Soviet Union analog. During the Romulan conflict neither the Federation nor the Romulans had video capable FTL radio so all contact was via voice or text. No one had seen a Romulan until the incident. Of course "Enterprise" threw that all out the window.