Going by the cliches of the genre, the assault on Perth is scheduled for either during the school's combat tournament to decide who's Vanguard, or during the end of year ceremony. Given that this is a -1 world there's going to be a number of dead Valkyries, civilians and soldiers before the attack is turned back through the amazing theme music power up of the protagonist (and optionally his squadron).
Not if we break the genre *cackling*
Ceterum autem censeo Type Zero Abraxas esse delendam.
We can win by force of fucking
Dakka, and the place to start is Space. We destroy class A type zero Abraxas, and suddenly we have all kinds of orbital capabilities. Then we either complete the Ginnungagap project or we bomb the ever-loving *expletive deleted* out of the American majors. The former is a win path presumably ending in a fight against a Class S while the project's result gets ready to
Dakka Dakka the AGs straight to hell. The latter is a win path by straight force of arms; the American majors are the furthest from other majors and therefore
probably more vulnerable, but their destruction would close fronts all
over the place. Think taking out Japan in WWII before the Germans, if the allies actually had to commit significant forces against Japan and China was a critical part of the war effort. Suddenly the entire 300 can be sent to Eastern Europe + Africa. And we still have the orbitals.
... Woah, where did that come from?
But yeah Perth is probably getting attacked... Unless
like everything else in this quest the plot differs from normal harem anime by having things make sense. We could get called away at any time as Coroner. Kouji and co could sneak away and try to miraculously save us. The flight could get rotated to the front with two combat-veteran aces on it. The international tournament thing could bring us closer to the front.
Well, you want a big fight scene that probably won't play out in the quest and lots of Anna? How about an antagonist attack on Perth? Especially if the instructors are wounded/dead/elsewhere/otherwise incapable of helping, and Anna and the other veteran cadets have to rally the younger students?
I pictured it as someone talking to a flight member in front of Koujirou.
Uh.
Hm.
Yeah, this could work... I'd have to have an AG kill Kouji, though.