Why were the Imperials rude to Vader in the beginning of A New Hope?

Question

It was my understanding that Vader was the second in command of the Emperor in the Empire.

However in the beginning of the movie one of the generals taunts Vader that his abilities in the Force have not been able to help him find out about the rebel base nor help him retrieve the stolen Death Star plans, before Vader force chokes him for his disturbing lack of faith

After this another guy simply commands Vader to stop it, which he quietly obeys.

After this scene, through out the rest of the movie and the trilogy, they all act appropriately scared of him.

However, what happened in the beginning of the movie? Why were they somewhat rude to Vader? Were the generals of equal status to him? Or higher in the chain of command? Vader was still considered a powerful person, they should at least have been scared of him.

Answer 1

• Vader is outside the chain of command. He's not in charge of the military, even if he's a powerful member of Palpatine's inner circle.

  • Also, whether he's the second most powerful or not is kind of hard to determine, because (by Emperor's design) power in the Imperial top is a pyramid, not a well-ordered set. Palpatine intentionally set up different competing power centers, as checks-and-balances against anyone conspiring against him (Vader; Xisor; Council; Military-industrial heads; Emperor's Hands; senior military officers; Moffs; Inquisitors are just some of the poles vying for power under him).

• And, likely, outside their personal political camps (and high level brass, especially in an autocracy, is inherently a set of political enemies, aiming to gain more power). We can see that clearly shown in New Disney Canon novel "Tarkin", and there's merely 5 years after Clone Wars ended.

• Not everyone is aware of Vaders personal Force-fueled power. We see in New Disney Canon novel "The Sith Lords", where most people have very little clue of just what The Chosen One Creepy Anakin is capable of. There don't seem to be many witnesses left once he's done demolishing opponents (also seen in Tarkin)

Answer 2

Vader's authority in the Empire was generally superseded only by the Emperor's. However, Vader's authority was also superseded on the Death Star itself by Grand Moff Tarkin (the guy who commanded Vader to stop using Force Choke). Wookieepedia's Death Star article cites the canon reference book Star Wars: Absolutely Everything You Need to Know in stating that Tarkin was the commander of the Death Star. Tarkin was put in charge of the Death Star at the same time he was given the rank Grand Moff:

“We need to tighten our hold over the Outer Systems,” the Emperor continued. “You will be in charge of that, Moff Tarkin. Or should I say Grand Moff Tarkin. ... The Outer Rim is yours to oversee -- and with it, Grand Moff Tarkin, the whole of the mobile battle station project.”

_{Tarkin, p. 248}

Notably, Vader was present for that conversation -- so Vader was fully aware that Tarkin was in charge of the Death Star.

Since Vader was not the ultimate authority on the Death Star, Admiral Motti evidently felt safe enough to taunt Vader in the presence of Tarkin. Furthermore, Motti taunted Vader because the power of the Death Star was obvious yet Vader's power from the Force was not so evident:

Motti: Any attack made by the Rebels against this station would be a useless gesture, no matter what technical data they've obtained. This station is now the ultimate power in the universe. I suggest we use it!

Vader: Don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant next to the power of the Force.

Motti: Don't try to frighten us with your sorcerer's ways, Lord Vader. Your sad devotion to that ancient religion has not helped you conjure up the stolen data tapes, or given you clairvoyance enough to find the Rebels' hidden fort...

Afterward, the Imperials acted appropriately scared since they had seen Vader's power firsthand.