(Chris Rukan/The Washington Post)

I always planned to spend much of 2017 thinking about the Vietnam War. In the summer of 2016, I began to report a major project on Ken Burns and Lynn Novick’s documentary about the conflict, which set me up for 15 months of reading all the major books about the war, interviewing soldiers who fought in Vietnam and scholars who studied American involvement there, and even traveling to the country for 17 days in February.

But the presidential election plunged the United States deeper into one of the most divisive periods since the Vietnam War ended. That irrevocably changed the nature of my series — and spending the year since the election thinking about the war has changed how I see our present moment in ways that make me both more and less optimistic.

The Vietnam era is a reminder that the rancor that currently characterizes our politics and culture isn’t new to the national landscape. Fifty-eight percent of Americans blamed the students at Kent State after the National Guard opened fire on antiwar protesters, killing four people and wounding nine. That’s disheartening, but it also tells us that our country has survived this level of internal contempt before.

“One of the great ideas of the last hundred years has been, does American democracy work?” Thomas Vallely, who served with the Marines in Vietnam and now works to improve higher education there, told me. “And Vietnam is a pretty good example that it’s pretty resilient.”

That’s true, to a certain extent. America did eventually leave Vietnam. The New York Times and The Washington Post’s publication of the Pentagon Papers allowed Americans to confront the extent to which their government had lied to them, ending a dangerous era of unquestioning trust in federal authorities. Despite the convulsions that racked the United States, spurred not by only the war but also persistent racial inequality, we did not become a military dictatorship. After his criminal obstruction of justice was exposed, Richard Nixon resigned the presidency, saving the United States from a constitutional crisis. If we withstood these threats, perhaps we can make it through a new era of instability.

To make "The Vietnam War," Ken Burns and his collaborators had to confront their own memories. (Adriana Usero/The Washington Post)

At the same time, studying the Vietnam War also reveals the cost of that resilience. Burns and Novick kick off “The Vietnam War” with a sequence that includes former secretary of state Henry Kissinger declaring that Americans need to “heal the wounds and put Vietnam behind us.” It seems clear that we followed up on only the latter half of that equation. And our failure to truly repair the lacerations of that era — to reconcile veterans and protesters, to really address racial, economic and gender inequality, and to draw the line between healthy skepticism and cancerous paranoia — contributed to our descent into a state of conflict that may be even more dangerous than the Vietnam War was.

While “The Vietnam War” was airing, I heard from readers who were still profoundly affected by the experiences of family members who had been prisoners of war; by what they had been unable to accomplish in Vietnam as soldiers and in the United States as civilians advocating for social change; and by their uneasy truces with their neighbors, as veterans and protesters unable to discuss their experiences with each other.

We didn’t have the skills or the national will to address these injuries before they turned into permanent scars. And I don’t know that we have the resources to do the work of reconciliation now, after those scars have festered for five decades and more have been added to our collective psyche. Whether we’re talking about people who supported or opposed the Vietnam War or reckoning with whether it’s even possible to get Trump voters and Clinton voters into rational conversation with each other, we’re asking the same fundamental questions. America’s resilience during and after the Vietnam War provided us with a semblance of national coherence, but it didn’t give us a workable answer.

More than anything else, exploring the Vietnam War reinforced my sense that while American history revisits the same patterns, it doesn’t repeat itself — not exactly. Instead, we circle back to the work we didn’t quite complete, finding that our patch jobs are riddling with new cracks all the way down to our foundation. The enmities of the past are rarely vanquished. They just reinvent themselves, whether in the form of tiki-torch-wielding white supremacists or bitter debates over respect for the military that are now tangled with the National Football League’s corporate image. We’re fighting the ghosts of Vietnam in the Trump era, even as his presidency begets more ghosts to join their numbers.