The arrival of the cavalry is a classic moment in many stories. But you don't have to play by the standard formula of them arriving at the moment of greatest need and saving the day. You can have them refuse the call to come and help. Or they could arrive too late, after the heroes have somehow triumphed without them when they didn't get there earlier. Or the hoped for assistance could turn out to be illusory as the reinforcements that arrive join the bad guys!
Or for another variation, the one in this comic: The cavalry arrive early, but there's some complication that means they can't render as much assistance as you'd expect, thus throwing out another problem for the heroes to solve.
[Reminder: Our guest commentators have not seen Rogue One. Part of the fun is seeing how their untainted impressions re-interpret the movie through the lens of our comic.]
Forgot our power converters?
Just opening the door and letting Rebel fighters in?
So... how come they haven't just owled hand-grenades to the Ministry workers and wiped out the magical Britain government in one weekend? Oops, sorry, wrong fanfic.
Again I have to wonder how it is that the Rebellion hasn't won already.
The Empire has to be one of the most laughably incompetent organisations that I've ever seen.
The can't train their soldiers to shoot straight, they have no concept of workplace safety (resulting in frequent reductions in the workforce) and they have some of the dopiest guards in existence.
It makes one question the Rebels.
GM: Cassian, you receive a radio signal. The Rebel fleet has arrived!
Cassian: Huh. The Council must have finally made a decision.
Admiral Raddus: Rouge One! Admiral Raddus here. Jar Jar told us where Toprawa was. But how did you get through the shield?
Bria: Oh, the gate guys let us through.
Admiral Raddus: We see it! A cargo ship is entering. Can you make sure they don't close it?
Cassian: Uh... maybe. But you should send fighters through right away.
Bria: Hey gate guys, it's us again!
Imperial Gate Guard: Um, we kind of have a situation at the moment. Can you call back later?
Bria: That's what we're calling about. We forgot our power converters, and we're just bringing them through in those ships now.
Imperial Gate Guard: Rebel fighters?
Bria: Ah!! You noticed! Well done! I'll be sure to note your superior observation skills in my report.
Imperial Gate Guard: I'll make Head Gate Guard yet!