Ive mentioned this in replies but wanted to bring it to a greater context.
With the blantent horrible decision of the 'Dark Political group' releasing Jhin (an Ionian serial killer - as in he terrorized Ionia only) makes me 100% confident that this political group wants Ionia to fall to Noxus in the invasion. Why would any native Ionian want this? That got me wondering, the Black Rose is mainly political subterfuge so what if the Black Rose infiltrated the Ionian government by either members or mind control/propaganda?
Also, what if - since we know the Black Rose and Noxus are not one in the same but two seperate entities, the Black Rose started the Ionia/Noxus conflict to further some political agenda/gain power (not dissimuliar from how the Nazi party used anti-jewish propaganda after WWI to gain popularity - because alot of Germans at the time blamed Jews for the loss of WWI).
So maybe the Black Rose is pupeteering Noxus to invade Ionia because there is something in Ionia they desire?