Catplayz
Bypassing the interdict fields, a number of small capsules, no more than a dozen, appear over important Federation shipyard and manufactory worlds. They look scorched and somewhat damaged, no doubt whatever foul sciences allowed them to breach the interdict was a one-time thing. Nimbly dodging the orbital defenses that shoot at them, some enter atmo and detonate, some smash in orbital shipyards. All of them release a thick noxious black goo on exposure though, that eats into Kel'Shir ships and buildings, and twists any populace exposed to it beyond recognition. Material exposed to it tarnishes and begins to dissolve, the nano-weave of Kel'Shir tech undone by the substance.
This is the first shot of a war, but who is the aggressor? (Out of RP spoiler alert, I'm coming for round 2, @Catplayz . Get your big boy pants on, we gonna rumble.)