The principle of civilian control forms the foundation of the American system of civil-military relations, offering assurance that the nation’s very powerful armed forces and its very influential officer corps pose no danger to our democracy. That’s the theory at least, the one that gets printed in civics books and peddled to the plain folk out in Peoria.

Reality turns out to be considerably more complicated. In practice, civilian control—expectations that the brass, having rendered advice, will then loyally execute whatever decision the commander-in-chief makes—is at best a useful fiction.

In front of the curtain, the generals and admirals defer; behind the curtain, on all but the smallest of issues, the military’s collective leadership pursue their own agenda informed by their own convictions of what is good for the country and, by extension, for the institutions over which they preside. In this regard, the Pentagon’s behavior does not differ from that of automakers, labor unions, the movie business, environmental groups, the United States Conference of Catholic Bishops, the Israel lobby, or the NAACP.

In Washington, only one decision is considered really final—and that’s the one that goes your way. Senior military officers understand these rules and play by them. When the president or secretary of defense acts in ways not to their liking—killing some sought-after weapons program, for example—they treat that decision as subject to review and revision.

To overturn or modify a policy they judge objectionable, military leaders forge alliances with like-minded members of Congress, for whom the national interest tends to coincide with whatever benefits their constituents. Senior officers also make their case by working the press, not infrequently by leaking material that will embarrass or handcuff their nominal superiors.