The popular British sketch comedy show That Mitchell and Webb Look opens with a sketch set during World War II in a Nazi base on the Eastern Front. One solider approaches another with a quandary about their uniforms. "Have you noticed that our caps actually have pictures of skulls on them?" he asks, pausing before the punchline:

"Hans, are we the baddies?"

The gag works, of course, not just because the Nazis were indeed the "baddies," but because, for the better half of a century, they have become definitive of "baddie" in the public imaginary — the zenith of evil against which all other forces for brutality are judged. John Milton was able to save even Satan's reputation, but Hitler as a figure representing evil is rightly beyond revisionism.

It is a sign of the simplicity of US political discourse emanating from inside the Beltway that comparisons to Hitler and the Nazis are consistently made to denote an enemy force. This past week, as international concern piqued about the rise of the Islamic State in both Syria and Iraq in light of the vile execution of photojournalist James Foley, the US dealt the Nazi card. In a tweet from a State Department account, two pictures were juxtaposed showing a near identical scene, separated by more than 70 years. In one, Nazi soldiers execute men kneeling over a pile of corpses; current Islamic State fighters are shown doing the same in the second image.

It was a cheap move by the State Department, to remove two such violent images from context and equate them by virtue of little more than visual similarity. It's true, both images depict unspeakable brutality, but by invoking the Nazis, the US government makes its line on the Islamic State as nuanced as a sledgehammer. In American political oratory, a Nazi or Hitler comparison is the ultimate in establishing an enemy in need of fighting. After all, who could turn a blind eye to the Nazis?

To be sure, there are comparisons that hold up between Hitler's National Socialists and the Islamic State. Hitler's aims were expansionist and included the extermination of whole races and religious groups in the establishment of an empire. The Islamic State, too, aims to spread, exclude, and exterminate en masse. The Islamic State's leader, Abu Bakr al-Baghdadi, commands Fuhrer-level loyalty, despite (or perhaps owing to) his elusiveness.

But to spend time delineating specific similarities and differences misses the point of why the US invoked the Nazis when talking about the Islamic State. The proposition is simply, "They're the worst." Nazi comparisons in contemporary political discourse have form but no content. They are question begging: Do you want to be the ones who didn't stop the Nazis?

I see something profoundly patronizing in the invocation of Hitler and Nazis when talking about a contemporary (and terrifying) political force. The oratorical tool suggests that the public cannot judge the threat of the Islamic State on its own terms, that it is not enough to observe their murderous tactics, swift rise, and ideology of hate. Add to this an access to money unprecedented among other contemporary terror groups; "the Taliban with oil wells," as Bloomberg put it. Indeed, with the Islamic State's powerful propaganda machine at work, it makes its ruthlessness plain to see, no Nazi comparisons necessary.

But an invocation of the Nazis or Hitler is a political act that goes beyond a description: It's an inexorable call to arms. The subtext of any Nazi comparison by a US official is to invoke a moral obligation to engage militarily. A look at post-Cold War US military theaters tells us as much. In advance of the Gulf War in 1990, President George H. W. Bush compared Saddam Hussein's invasion of Kuwait to Hitler's invasion of Poland. He delivered the analogy as if talking to a primary school class: "I'm reading a book, and it's a book of history, a great big history about World War II, and there's a parallel between what Hitler did to Poland and what Saddam Hussein has done to Kuwait."

To venture into yet more war in Iraq after a decade of ruinous military engagement, the US must frame an enemy too evil to ignore. Not just Nazis — apocalyptic Nazis.

Media scholars William A. Dorman and Steven Livingston traced the political resonance of the Hitler-Hussein analogy. They note that following the US invasion, between August 2, 1990 and January 15, 1991, there were 228 articles published in the New York Times and the Washington Post that drew on the Hitler comparison. According to polls at the time, public support for the war was not grounded in sympathy for Kuwaities, but in antipathy for the Hitler figure, Hussein.

Dorman and Livingston usefully highlight the political work done by Nazi comparisons. For one, in complicated terrains like the Middle East, a Nazi analogy simplifies the discourse. It also problematically shuts it down: If it can be established in the public imaginary that a force is as bad as the Nazis or Hitler, then arguments for ignoring or appeasing that force get swiftly foreclosed. It's a near-sure-fire pretext for war — reductio ad Hitlerium.

Another effect of Nazi analogies relies upon an assumed shortness of public memory and geopolitical ignorance. After all, if Hussein had been an evil comparable to Hitler, why had the US provided help to the dictator during the Iraq-Iran war, during which Iraq was known to have deployed chemical weapons, 10 years earlier? To invoke recent history of US involvement in the Middle East was to implicate the US in current horrors; better to reach back into history and across continents to maintain US purity and talk of Hitler.

It's a strategy seemingly torn from the pages of 1984, in which perpetual war shifts between Oceania, Eurasia, and Eastasia; the once trusted ally becomes the sworn enemy, and the public accepts the new configuration as a timeless truth. We see the same today, when discussion about America's ultimate failure in Iraq and subsequent de facto arming of the Islamic State gets hushed under booming proclamations about the unique threat posed by these highly organized extremists. US rhetoric surrounding the Islamic State goes further than the "us versus them," Straussian formulation of a typical geopolitical enemy; this group is, as Defense Secretary Chuck Hagel put it, a force that cannot be contained "in perpetuity" — he called their vision "apocalyptic" and spoke of "end times."

American bombs and missiles began striking Islamic State targets days after the militant fighters took control of the Mosul Dam and a series of oil fields. The group had been massacring and indoctrinating before that, of course, but nothing ignites rhetoric about monstrous enemy forces like a threat to oil. To venture into yet more war in Iraq after a dishonest decade of ruinous military engagement, the US must frame an enemy too evil to ignore. Not just Nazis — apocalyptic Nazis.

(It is worth noting that Pentagon officials are correct in their description of the Islamic State as a force the likes of which have never been seen before. I don't mean their threat or brutality is unparalleled. Rather it's true that we have never seen a force like this before — they are unique in making themselves visible. They publish execution videos, they occupy social media platforms; they are terror in plain sight. If anything, this should be counterposed, not compared to the Nazi propaganda machine, which projected images of glory, victory, and nobility. The Islamic State speaks in a visual language of violence, destruction, and domination. And this is the worst force we've seen insofar as we have the technology to see and they have the technology to be seen.)

There is some complex realpolitik facing the Obama administration in Syria. Just one year ago, discussion of US foreign policy was littered with references to the "red line" crossed when President Bashar al-Assad used chemical weapons. One year ago, Assad got the Hitler badge. "Bashar al-Assad now joins the list of Adolf Hitler and Saddam Hussein who have used these weapons in time of war," Secretary of State John Kerry said last September. Today, there is consideration (as yet undecided) of an allegiance with Assad's forces to defeat the Islamic State. The force of a Nazi comparison is somewhat weakened when, within the space of a year, a Hitler is poised to become an ally.

It's as Edgar reminds us in King Lear: "The worst is not, so long as we can say, 'This is the worst.'" Meaning, as long as we are alive and in the position to call something "the worst" — or "Hitler" — certainly our situation is not yet the worst. But in the rhetorical playbook of American war-waging, there is scant regard for the logic of superlatives: Our war machine leaves room for an enemy to be the worst, and a new enemy to be worse than the worst. If we've spent our Nazi analogies, and there's no "worst" to speak of, the US war drum will beat louder still, sounding nothing short of the end of the world.