(WARNING: This article contains spoilers for Rogue One. Proceed with whatever level of caution the Force suggests to you is wise)
Rogue One welcomes us back to our beloved galaxy far, far away — and in doing so, it reintroduces us to the galaxy's darkest days. When we were introduced to the Empire in A New Hope, they were a formidable military force. In Rogue One, we finally get a sense of the might of the Empire!
Welcome To Scarif
Described by StarWars.com as "the principal construction facility for the vast Imperial war machine," Scarif is a beautiful jungle-world that's marred by the Imperial presence. Giving a sense of the lengths the Empire will go to in order to secure their military might, the entire planet is protected underneath a planetary shield. Rogue One gives us an idea of just how powerful that shield really is — it only falls when two Imperial Star Destroyers collide with the gate portal.
Personally, I found this absolutely chilling. Remember that, although there are pockets of resistance on worlds such as Jedha, until this point there's been no organized Rebellion. In spite of the fact that their enemies are in disarray, the Empire will go to any lengths to secure its facilities. In the case of Scarif, the planetary shield is up all the time — an entire world cut off by a shimmering field of energy. Imagine the power required for something like this.
The Tarkin Doctrine
"This bold vision of the future requires not only the service of those of immaculate reputation and consummate skill in the just exercise of power, but also the service of a vast military dedicated to upholding the laws necessary to ensure galactic harmony. It may appear to some that the enactment of universal laws and the widespread deployment of a heavily armed military are steps toward galactic domination, but these actions are taken merely to protect us from those who would invade, enslave, exploit, or foment political dissent, and to punish accordingly any who engage in such acts. Look on our new military not as trespassers or interlopers, but as gatekeepers, here to shore up the Emperor's vision of a pacified and prosperous galaxy."
Grand Moff Tarkin is credited as the mind behind the "Tarkin Doctrine," which stresses the necessity of a strong military to keep peace across the galaxy. Tarkin believed that the only way to secure peace was for the Empire's might to be so great as to terrify all who would dare oppose it. In this doctrine he expressed similar beliefs to the Emperor himself, explaining both Tarkin's ascension (he was the first Grand Moff) and the Death Star's construction.
It's incredible to see, though, that Orson Krennic is willing to fire the superweapon at Jedha the moment it's complete. He understands the Tarkin Doctrine, and embraces it; the superweapon will only generate the appropriate amount of fear if the Rebel Alliance knows that the Empire is willing to use it. In the end, though, Krennic is simply told to use the superweapon to destroy the Temple City of Jedha, before it is later used on Scarif too. It's rather like using a tank to crush an ant — a use of overwhelming power to engender terrible fear. That's especially the case on Scarif, where the Empire essentially sacrifices a major Imperial facility just because there are a handful of Rebels on the ground.
Of course, the Empire ultimately does not flinch from using the Death Star. As all #StarWars fans know, the Empire eventually makes an example of Alderaan, a heavily-populated planet. The entire world is summarily destroyed because of the rebellion of Senator Bail and Leia Organa.
You Don't Cross The Empire
I love the boldness of Rogue One. In this film, to cross the Empire is to die. Rebels cause problems on Jedha? The Empire destroys the entire planet. When the Rebels attack Scarif, AT-ACTs are brought in, and the Rebels eventually fall to the overwhelming waves of Stormtroopers. Realizing there's a chance that the Death Star plans could be transmitted, Grand Moff Tarkin chooses to destroy Scarif's central Imperial installation.
I want you to consider just what Tarkin did there. That facility housed records for countless Imperial projects, not just the Death Star. However, because the facility is compromised, Tarkin is willing to destroy all of it.
Those last 15 minutes are electric, as the Empire brings in all its might to crush the Rebellion. We know the Death Star plans will escape, but as Darth Vader arrives at the forefront of the Imperial fleet, we realize that the odds are very much against the Rebellion. Frankly, it's luck rather than judgment that saves the Rebellion, with those plans hotly pursued by Darth Vader himself. The Sith Lord is relentless, ferocious, and lethal; he cuts a swathe through Rebel forces, not even seeming to exert himself as he does so.
Rogue One gives us a glimpse of an Empire that has good reason to stand confident in its military superiority. The Empire's might is palpable, and, guided by the Tarkin Doctrine, it will go to any lengths to triumph and engender fear across the galaxy. It's telling that the Rebellion doesn't initially send a team to Scarif for the plans; the Council can't agree because they are terrified of the power of the Death Star. If not for a handful of Rebels who refused to accept defeat — and were even willing to give their own lives — the Empire's might would have won the day.