Power dynamics within the US military are largely unique from those within civilian organizations for several reasons. They also differ somewhat in expression across different units and branches of the military.
Generally speaking, power within the military is structural, conferred by rank and position. This power, which generally scales with rank, can be vast at the higher levels of command. High-ranking officers typically command thousands of servicemen, controlling not just their work but many aspects of their lives. When Gen. Mountcastle was the commanding officer of an armored brigade stationed in Germany he was essentially running a small town. He was not just in charge of military matters, but also the other concerns involved with maintaining such a large unit such as housing, transportation, and family matters for thousands of individuals. This is a lot of power, and he was only in charge of a brigade (a brigade consists of 3000-5000 men; A division consists of three or more brigades, with a total manpower of around 10,000-12,000; A corps consists of two to five divisions; thus, a corps commander has a LOT of power).
This power, however, is far from absolute. The military hierarchy is well-designed to prevent absolute power and the abuses that tend to go with it. Nobody in the military, no matter how high in rank, has absolute power. This is because everybody in the military reports to someone else. There is no single person with absolute authority besides the President, who is not a part of the military and thus not worth discussing. This was something emphasized by practically everyone I interviewed. No matter how much experience you have, no matter how high your rank or influence, there is always somebody above you and you are always following orders. A corporation can be brought down by a bad CEO abusing the near-absolute power of his/her position (especially if that CEO is also the primary shareholder). In the military, however, a bad officer who abuses their authority, no matter how powerful, is always accountable to somebody and can at any point be removed from their position.
There is so much competition for positions and promotions that anyone can be replaced. This largely ensures that an officer’s first concern is the needs and well-being of the military, rather than their own. People are granted immense power, but only on the condition that they will use said power exactly as the US government needs them to.