The highest-ranking U.S. military officer is ordering commanders to tread carefully during the current presidential campaign—even if their expertise could correct misguided ideas about national security.

This presidential campaign has introduced some of the boldest—some would say craziest—national security proposals, including reinstituting torture, defunding NATO, and bombing the self-proclaimed Islamic State until “sand glows in the dark.”

For Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, the increased call on the military to referee campaign ideas is such a problem that he has quietly urged commanders to stay out of the political fray. This week, he is expected to also issue a memo outlining to generals how to navigate the current political discourse.

He will remind generals that their assessments could become political fodder, even if they don’t intend it that way.

The military, Dunford argues, must retain its place as a non-political force that offers its best military advice to whatever party the commander in chief comes from.

There is an expectation that military commanders are supposed to give their honest assessment. And Americans say they see the military as the only apolitical, relatively honest arbiter on national security matters. Perhaps because of that, when the candidates fall short on specifics, it often falls to the military to provide the kind of measured nuance missing on the campaign trail.

Indeed, each time a general has nixed an idea that has popped up during the primaries, it has all but disappeared from the political discourse. On Feb. 1, for example, Lt. Gen. Sean MacFarland, the commander of the U.S. campaign against ISIS, rejected Republican Sen. Ted Cruz’s idea of carpet-bombing ISIS.

“At the end of the day, it doesn't only matter whether or not you win, it matters how you win. And we're the United States of America and we have a set of guiding principles and those affect the way we as professional soldiers, airmen, sailors, Marines, conduct ourselves on the battlefield,” MacFarland told reporters. “So indiscriminate bombing, where we don't care if we're killing innocents or combatants, is just inconsistent with our values.”

A month later, Lt. Gen. Charles Brown, commander of U.S. Air Forces in the Middle East, was more direct:

“Carpet-bombing is not effective for the operation we’re actually executing because we’re using precision-guided munitions on a regular basis,” Brown told reporters at the time. “And, on top of that, as you look at the ... law of armed conflict and us trying to minimize civilian casualties, carpet-bombing is just, in my opinion, not the way to go.”

Dunford himself unintentionally became the part of the discourse when a reporter asked him whether NATO was obsolete, referring to Republican presidential candidate Donald Trump’s assessment in a meeting with the Washington Post editorial board.

Dunford answered the question, not realizing Trump had proposed it, saying, “In my mind, the relevance of NATO is not at all in question.”

That he was presented as rebutting Trump inspired his push to keep the military out of the fray.

But can the military really be extracted from American politics? Of this country’s 44 presidents, 12 have been former generals, albeit retired by the time they took office. In recent weeks, some have suggested that Ret. Gen. James Mattis, the former Marine Corps commandant, run for office.

And the kind of national buzz about America’s next president has hardly spared the Pentagon, where some are threatening to resign, depending on the outcome.

Indeed, retired generals now are part of campaign staffs.

The very civilian leaders that are supposed to keep the military above the political fray sometimes exploit their standing instead. It is hardly rare that politicians trot out those in uniform to give credence to their policy. During the 2007 surge in Iraq, for example, Gen. David Petraeus, then commander of the war, was the face of war for the Bush administration, which by that point suffered eroded creditability.

Near the end of the Gulf War, then-Gen. Norman Schwarzkopf, the exultant commander, gave what was called the “Mother of All Briefings” as he walked the American public through the military strategy, using Power Point and phrases like “Hail Mary” to explain the U.S. strategy. The briefing eventually was sold nationally on a videocassette, and the briefing became the defining explanation of the war.

Moreover, today’s general is often a politician as much as a military tactician. Last month, when reporters asked Air Force Gen. Philip Breedlove, the NATO supreme allied commander, about the effectiveness of torture, he sought to dodge the political debate, noting that European leaders turn to him for guidance on the U.S. political process:

“Rather than address any single element and to stay clearly out of a political sense, I would just tell you that I get a lot of questions from our European counterparts on our election process this time in general. I think they see a very different sort of public discussion than they have in the past, and I think I’ll just leave it at that.”

Christopher Preble, vice president for defense and foreign policy studies at the Cato Institute, explained that generals cannot control the context in which they explain war, particularly during an election year. So they must tread a thin line of giving their best military advice knowing that it could be exploited.

And so long as the American public extends a kind of blind deference to military commanders and their thoughts on war, the apolitical military will be harder to maintain.

“Public deference to the judgment of military professionals has become a problem. All of the respect the military has is understandable. But it’s as though if a military officer endorses an idea then it must be a good one. That is not necessarily the case,” Preble explained to The Daily Beast. “The military is the most respected institution in the country, higher than organized religion. So, in that sense, we are all to blame.”