u/Porecomesis_

Ever since Volume 8 had Salem royally beating the tar out of Atlas with what is basically a full-scale direct Grimm invasion, many have asked "Why doesn't she just do that all the time?"

It's a fair question; Atlas' military might has been recognised the world over as early as Volume 2 and Ironwood's ultimate goal has been to assemble a military force capable of destroying Salem and her Grimm no matter how many holes he has to leave in Mantle's walls to do it.

It stands to reason that, if Salem can defeat the world's mightiest military in a direct contest of force, she could just... do that to all the other nations and take their Maidens and Relics without all this subterfuge.

I argue that she indeed can do this and succeed... but bulldozing kingdoms doesn't get her what she wants.

According to Ozpin, Salem's plan is indeed to get the world destroyed by bringing the four Relics together to call the Gods to Remnant and show them that the world is divided and must be destroyed, and her along with it. A sound plan with a major hiccup; as Salem has personally experienced, the Gods are fickle and easily ticked off by being played. If Salem just flattens the kingdoms to get the Relics and then goes "Look, here are the Relics, humanity's divided, can I die now?", then odds are that they're just going to put her in a gacha ball and throw her into a gumball machine for being so transparently deceptive. For any plan, never bet on Gods agreeing with you.

So Salem's course isn't to win; it's to make Ozpin lose. She needs plausible deniability.

While Atlas has proven she can indeed dump Grimm everywhere and just take whatever she wants, the important thing is for humanity to be divided for the Gods to actually do what she needs them to do. If she kept steamrolling kingdoms, it's more likely they'd unite in the face of her overwhelming and destructive threat. Hence, her plans hinge on turning humanity against itself, such as how Cinder used the Vytal Festival to make hunters look brutal and bad.

I say that, however... if that was true, then shouldn't Salem have been unable to bulldoze Atlas like I just said? Well, Atlas is an exceptional kingdom by its own design; it has spent decades sabotaging the other nations for its own empowerment so that it was isolated on the international stage. Even the nation itself was beset by its own partisan politics because Atlas was leaving its own people cold to bolster its own military, nevermind other nations like Vacuo.

The fall of Atlas, having stranded itself, made Salem's onslaught feel more like an outlier and exceptional circumstance. That exceptional circumstance does not exist for Vacuo and, besides, Ruby's message has alerted the world to the fact that she exists and that Salem is organising the Grimm to destroy humanity. She can't hide behind Vacuo's vices to run roughshod.

So here we are. Humanity is holding out in Vacuo and relations are tense. Still, everyone's surviving together for now, fighting off Grimm and protecting whatever they can because there's nowhere else to go (one might say Mistral but, for the sake of discussion, let's just take the show's word for it). On top of that, they know Salem exists and is bearing down on them. If there's one thing humanity is at this stage, it's united, and an invasion is just going to reinforce that.

Enter the Asturias twins. Salem couldn't have asked for better pawns. How else to turn humanity's last stand against itself by brainwashing the close-knit community and literally making them turn on each other? If Salem can stir up distrust and despair by getting to key members of the resistance and making them fight the rest, then humanity will be divided while she finds the Maiden and the final Relic and gets ready to bring the set together to show the Gods her handiwork.

Salem does have the forces to bring Vacuo to its knees. She could destroy humanity herself. But that's not what she wants; she wants the Gods to come down and break her curse themselves and she's not going to accomplish that by force.