Also this is a personal thing but I'd switch up my GMing and give the game a constant mission based format, to keep things exciting. Bad things should happen to UMMA every once in a while to encourage them to stay active. Basically nothing bad has happened to that side at all, so I'd do something big. I'd also clarify SE's major/minor goals, and make sure its missions relate to those in some form or another.

I think UMMA and SE both have NPC leaders. They should designate a few PCs on each side as "Generals", and have said generals arrange missions for each side, designating where their players need to go.

UMMA should have a major concern in controlling collateral damage from various battles. Conversely, SE can use raids and terror attacks to serve as bait while it goes on other missions.

NPCs shouldn't have too much power as far as getting missions done is concerned. That power should lay in the players' hands. Otherwise, you take away player agency, which is super toxic for any game.

Both teams should manage where they send agents of varied powerlevels to counter the other's missions. If you send weak UMMAgents to the wrong place, then SE will win. But if you have to many gather in one world or waste an overpowered UMMAgent, that would allow SE to easily assault another, undefended world, for example.

Both teams should also focus on recruiting neutral characters to bolster their ranks, as well.