Myth #7: War is the continuation of policy by other means.

A US Army OH-58 Kiowa helicopter provides aerial support for US soldiers patrolling with Afghan National Army soldiers, February 28, 2012. US Army/Sgt. Christopher McCullough

So, in a riff on Prussian military theorist Carl Von Clausewitz's famous maxim, generations of American statesmen and military officers have professed to believe. Yet, in the present century, the challenge of making armed force politically purposeful has turned out to be daunting. Nothing illustrates the point more clearly than America's never-ending war in Afghanistan.

Like the clutter of online ads that our eyes automatically ignore, Americans have learned to tune out this longest war in our history.

Originally styled Operation Enduring Freedom, the war itself has certainly endured. It began when this year's crop of high school graduates were just leaving the womb. In terms of total length, it's on track to outlast the Civil War (1861-1865), US participation in the two world wars (1917-1918, 1941-1945), the Korean War (1950-1953), and the Vietnam War (1965-1973) combined.

The Pentagon has never demonstrated more than minimal interest in calculating the war's cumulative costs. While researchers do their best to keep up with the mounting tally, their numbers possess almost no political salience. Congressional Democrats get exercised about the handful of billions of dollars that Donald Trump wants to waste on building his wall, but few members of either party attend to the hundreds of billions wasted in Afghanistan. So like the Energizer Bunny, the war there just keeps on going, while going nowhere in particular.

In his State of the Union Address earlier this year, the president opined that "Great nations do not fight endless wars." It was a commendable declaration. Indeed, Trump has made it unmistakably clear that he wants out of Afghanistan as well as Syria, and the sooner the better. The boss has spoken: We're leaving, pronto, sayonara, gone for good.

Yet as is so often the case with this president, words have not translated into action. So, contrary to Trump's clearly expressed intentions, the Pentagon is planning on keeping 7,000 US troops in Afghanistan for another three to five years while also sustaining an active presence in Syria. In other words, the endless wars won't be ending any time soon.

There's a lesson to be learned here and the lesson is this: while senior military officers will never overtly disobey their president — heaven forbid! — they have evolved a repertoire of tricks over the decades to frustrate any president's intentions. On the eve of his retirement from office in 1961, President Dwight D. Eisenhower went on national television to tell the American people how it's done.

Credit the present generation of generals with having gone one further. Remarkably enough, they have inverted Clausewitz. No longer does discernible political purpose serve as a necessary precondition for perpetuating a war. If generals (and militarized civilians) don't want a war to end, that suffices as a rationale for its continuation. The boss will comply.

We can therefore thank Trump for inadvertently laying bare the reality of civil-military relations in twenty-first-century Washington: The commander-in-chief isn't really in command.