Gregory A. Daddis is director of the graduate program in War and Society at Chapman University and author of the forthcoming book "Withdrawal: Reassessing America’s Final Years in Vietnam."

Generals like Creighton Abrams play an important role in American foreign policy, but can’t replace civilian leaders. (AP/Horst Faas)

Fifty years ago, Americans were embroiled in a bitter and controversial war that divided a nation and cast doubt on their faith in the office of the presidency. We certainly remain drawn to stories of the Vietnam War, as evidenced by a newly released New York Times best-selling account of the 1968 Tet offensive and the popular buzz surrounding the upcoming Ken Burns and Lynn Novick documentary.

Without question, the American involvement in Vietnam reverberates well beyond the war that ended there in 1975. Perhaps most importantly, the experience demonstrates, then and now, our inflated expectations of generals as superheroes. The conflict created such a crisis of authority for the president that generals emerged as the nation’s new leaders, trusted agents to whom journalists and the public could confidently turn in a time of crisis.

But relying on generals to determine questions of war and peace creates unrealistic — and troubling — expectations for those same generals to craft policy and oversee, unchecked, a military that was intentionally designed to follow the command of a civilian.

Nowhere were these civil-military relations issues more evident than in the aftermath of one of the most significant campaigns of the entire war — the Tet offensive.

In late January 1968, military forces from the North Vietnamese Army and the National Liberation Front — popularly known as the Viet Cong — launched a countrywide offensive across South Vietnam. Hard fighting engulfed 36 of the country’s 44 provinces. Viet Cong sappers breached the walls of the U.S. embassy, engaging in a day-long battle with military police. In the Imperial City of Hue, house-to-house combat wracked the city so thoroughly that one witness called it “screaming and moaning in the throes of death.”

All the while, Americans at home watched in near disbelief. How could the enemy have launched such a powerful assault? Was the United States not winning the war? Might not a change be in order, where a new commander might step in and, with a better strategy, turn things around?

Change did come that summer, as Creighton Abrams replaced William C. Westmoreland as head of the U.S. military command, and many Americans discovered a renewed sense of hope about the war in Vietnam. Though President Lyndon B. Johnson had decided not to run for reelection back in March, the apparent lack of political leadership seemed not to matter.

Journalists wrote fawning profiles of Abrams in mid-1968, casting the cigar-chomping officer in heroic language and making him the symbol of a fresh start. A new general would come in and break the stalemated war. Isn’t this what American generals did? Had not Grant saved the Union for Lincoln? Didn’t Pershing sail to Europe to save the allies in World War I? Had not Patton reinvigorated the American fighting force in North Africa during the Second World War?

This faith in American generalship, however, was misplaced. In fact, the relationship between the Nixon White House and Abrams deteriorated to the point where the president twice nearly fired “Abe” for his ineffective prosecution of the war. Indeed, the general did not deliver victory.

While Vietnam continues to cast a long shadow over American foreign policy, the post-Tet period offers important perspectives for us as we consider the relationship between the president and senior U.S. military officers. In a time when our president has demonstrated a shaky grasp of foreign policy, Americans have increasingly seen retired marine general Jim Mattis and army lieutenant general H.R. McMaster as the wise adults in a White House filled with foreign policy neophytes.

“We have the greatest military in the world, and they’ve done the job, as usual,” said Trump after an April airstrike on an Islamic State position in Afghanistan. “We have given them total authorization, and that’s what they’re doing.” Many took comfort from this acknowledgment by the president that he was stepping away from the details of military operations.

But there is a problem here. In this narrative, civilian leadership matters little. Former general David H. Petraeus recently made the astounding claim that President Trump’s fitness to serve was “immaterial” because the senior military leaders around him were first-class. Apparently, if the generals are good enough, the civilian commander in chief requires no real presence in American foreign policy.

This is a dangerous way of thinking for all involved. Presidents can’t simply relinquish decisions on war or peace to their generals. As Eliot Cohen has persuasively argued, history indicates that grand strategy works best when predicated upon an open and honest dialogue between civilian overseers and their military commanders.

We have entered a moment in our history, however, where we have normalized a strategic dialogue in which only the military voice matters. This should give us all pause. And not simply because many find our current president erratic when it comes to questions of foreign policy.

We cannot simply assume that generals, through their own force of will, can win wars or alter foreign cultures with troop “surges” or magic strategic plans, much as we might want a Hollywood ending. Brad Pitt’s over-the-top character in the recent film “War Machine” may have excessively lampooned former general Stanley A. McChrystal. But the satire accurately depicted the egotism of more than a few senior military leaders who believe they alone can unravel the problems of American interventionism overseas. Abrams’s failure to end the Vietnam War is a warning against this perception of military omniscience.

Not only are generals not superheroes, they also can give really bad advice. Douglas MacArthur’s overreach in the Korean War, for instance, points to a misplaced public faith in hero generals and the limits of their power and judgment. And as Secretary of State, Colin Powell, a former chairman of the Joint Chiefs of Staff, hardly derailed the Bush administration’s plans for invading Iraq, rather offering public “proof” of Iraq’s weapons of mass destruction to justify one of the worst foreign policy mistakes in the early 21st century.

Crafting a grand strategy for the future requires more than just a professional military opinion. Our current concerns over what many see as an unfit president should not have us automatically turning to our generals to rescue us. Not only is this impractical, but it is unhealthy for the republic. A democracy that sees its military as the sole source of inspired leadership will not last long.

Without question, Mattis and McMaster are fulfilling an important service to our nation, as they have done throughout their distinguished military careers. But if history offers us any perspective on the vital topic of civil-military relations, they alone will be unable to restore a sense of normalcy to American foreign policy. Nor, on their own, can they establish political objectives that best sustain our national security and our democracy more generally. There are limits to what even the best generals can do for us.