Yeah, it's the first encounter with the Shivans. You're fighting some standard Vasudan fighters, they're roughly on the same tech level as you are, and then suddenly a bunch of red and black ships noone's ever seen before jump in and start massacring both sides. You can't lock them, they only show up on radar as faint whispers, they have shields and you don't, you're hopelessly outmatched. If you manage to down one anyway, you get a special medal.

The intro cinematic is basically the same thing and it's incredible. "Roger that pilot, we're sending a recovery craft now." "SEND FIGHTERS!" https://m.youtube.com/watch?v=NJ-xcgBL1mY&pp=ygUOZnJlc3BhY2UgaW50cm8%3D

The choice (or performance, really) that matters is a bit further in the campaign. At that point the Shivans are identified and you can lock them, and Humans are working with Vasudans, but they still don't have shield technology. One mission has you protecting a cargo convoy moving Human-Vasudan ship shield prototypes. You can still finish the mission if the convoy is destroyed, but then you have to keep playing with no shields. I think you end up getting them later anyway, but a failure to protect that convoy makes the next few missions way harder.

And then the final mission is a turkey shoot where noone can use their shields anyway, hehe