Had you asked my parents to identify the events that shaped the America of their time, they would have answered in unison and without hesitation. The Great Depression and World War II, which both experienced at first hand, cast their shadow over everything that followed and never lost their salience.

Pinpointing events that shaped the America of ourtime is more complicated. Our era has included its fair share of ostensibly momentous episodes, beginning with the fall of the Berlin Wall and Operation Desert Storm but also including the Clinton impeachment, the Bush v. Gore election standoff, the events of 9/11, the Global War on Terrorism, and the Great Recession. One after another, they come and then go. And once gone, they shrink in significance, even if still lodged in memory. Looming large in the moment—remember when Stormin’ Norman Schwarzkopf was compared to George Patton and the Lewinsky scandal ranked alongside Watergate?—the passing of even a handful of years cuts them down to size. They are not so much forgotten as subsumed.

For today’s young person, the Vietnam War lies as far in the past as Teapot Dome and the Scopes “Monkey trial” did for me when as a young soldier I deployed back in 1970. In other words, we’re talking about pretty ancient stuff.

In American Reckoning, Christian Appy, a professor of history at the University of Massachusetts, makes a strong case that even if Vietnam qualifies as pretty ancient stuff, it still matters a great deal. This year marks the 50th anniversary of U.S. combat troops arriving in South Vietnam, along with the start of Rolling Thunder over the north. But there the war sits, like some undigested lump caught in the nation’s gullet, stubbornly refusing to be subsumed. For better or worse, we live in its dark shadow.

Appy divides his book into three parts, devoting one each to reflecting on why we fought, how we fought, and what we have become as a consequence. Although the first two parts are insightful and instructive, anyone familiar with the historiography of the war will find few real revelations. Even so, crossing this well-trodden ground makes for painful reading. Appy writes with bite, anger, and outrage. To absorb his account is to imbibe those sentiments.

As to why, arguments offered up by the Kennedy and Johnson administrations, broadly supported by members of the political elite, that preserving South Vietnam constituted a vital U.S. national security interest—all the claptrap about domino theories and fighting in Southeast Asia to keep the Reds from invading California—have with the passage of time become simply incomprehensible.

Rising above all other egregious deceptions, at least in my mind, is the fact that American leaders knew thenthat the myth of monolithic communism was just that—a politically expedient figment of fevered imaginations. In reality, the Vietnamese hated the Chinese. For their part, the Chinese loathed and mistrusted the Russians. True, all three viewed the United States as an antagonist. Yet as President Nixon shrewdly if belatedly—perhaps even cynically—demonstrated, it lay within Washington’s capability to alter such perceptions. As a great power, the U.S. had options that it could exercise, given political leadership of sufficient wit and boldness. This fact retains considerable relevance in the present moment, with warmongers among us insisting that absent a recommitment of U.S. combat troops to Iraq ISIS will soon overrun all of Europe en route to creating a global Caliphate.

As to how, the more closely you examine the methods devised for prosecuting the Vietnam War—search-and-destroy combined with brutal but ineffective bombing—the more it becomes apparent that U.S. efforts were all but doomed from the outset. Having considered the range of possibilities available to them, civilian and military leaders chose the one least likely to yield success: a protracted war of attrition fought in a faraway land about which most Americans knew little and cared even less. By comparison, the Iraq War so recklessly begun and so radically mismanaged by George W. Bush and his generals almost seems a reasonable and well-conducted proposition—only by comparison, I hasten to add.

For my money, however, it’s part three of American Reckoning that breaks new ground and makes a distinctive contribution. When the Vietnam War finally ended in April 1975 with the fall of Saigon, President Ford had little interest in promoting anything remotely like a serious reckoning with the episode just then reaching its squalid and humiliating conclusion. Instead, Ford called upon Americans to undertake a “great national reconciliation,” as if all that had occurred had amounted to little more than an honest misunderstanding. “It was really a call for a national forgetting, a willful amnesia,” Appy charges.

Yet as his own account demonstrates, what ensued was not so much willful amnesia as willful misremembering. Americans didn’t forget Vietnam; instead they reimagined it.

Encouraged to avoid probing too deeply into matters likely to cause further pain and division, the great majority of the American people happily obliged. The upshot was not reconciliation but a sort of sham truce that papered over disconcerting questions about American purpose and identity that the war had raised. By converting the Vietnam War into a fraudulent parable, Americans succeeded in draining it of significance.

Misremembering, Appy writes, transformed Vietnam into a “story of American victimhood,” centered on specifically American sacrifice and suffering. The fate visited upon the people of Vietnam and neighboring countries gained little purchase in popular consciousness. While singling out a handful of designated scapegoats like Robert McNamara and William Westmoreland, Americans showed little interest in assessing the basic policy assumptions that had contributed to the debacle. Rather than viewing Vietnam as an outgrowth of systemic flaws, Americans classified the war as an inexplicable exception to an otherwise proven record of superior performance—the equivalent of a championship team having an off day. Certainly nothing that occurred in Vietnam offered reason to reexamine the capacity of the United States to lead the world. Any setback experienced there amounted to little more than an annoying pothole on the road to universal peace and freedom.

Needing heroes as well as scapegoats, this narrative of victimhood elevated American soldiers generally and POWs more specifically to a unique place of honor. Whether or not antiwar protestors actually spit on returning vets was beside the point. Some stories are deemed true not because they actually occurred but because they fill an essential need. Such was the case here.

Empathizing with those whose wartime service had gone unappreciated became a way of cleansing the landscape of complications. To designate all who served as heroes was to declare moot any further inquiry into conduct and consequences, whether individual or collective. Indeed, to make a show of praising those who served offered a sort of substitute for serving yourself. All that sufficed to demonstrate one’s credentials as a patriotic American was to stand with the troops, even if only figuratively.

The semi-sacred status acquired by the POW/MIA flag, promising “You are not forgotten,” signified something similar. Whether any POWs actually remained in Vietnam was irrelevant. The point of displaying the flag was to strike a posture.

Hollywood seized upon this sentiment with alacrity. POW movies starring the likes of Sylvester Stallone and Chuck Norris recast the entire Vietnam experience as a gallant effort to free Americans unjustly imprisoned by cruel and creepy Orientals. To liberate the captives was, in effect, to redeem the war itself.

Appy explores the significance of these films to great effect. Inferior art even by commercial standards, they brilliantly captured the mood of the moment. Over the past century, every decade has had its canonical cinematic depiction of what it means to be a pissed-off and alienated young American male. In the 1950s, for example, there was “Rebel Without a Cause,” and in the 1960s “Easy Rider.” After Vietnam, “Rambo” claimed the part. The political winds had shifted to starboard, but the basic point remained the same: you think I’m going to put up with this screwed up mess?

In a similar vein, Appy examines the fighter jock extravaganza “Top Gun,” which he identifies as perhaps the most important Vietnam War movie ever made, despite the nominal fact that it has next to nothing to do with Vietnam. Without question, the saga of Lieutenant Pete “Maverick” Mitchell—the un-Rambo—qualifies as one of the most enduring cultural artifacts of the Age of Reagan. It may be the perfect Reagan movie.

President Reagan’s singular political insight was this: he grasped—and fully endorsed—the unwillingness of Americans to acknowledge historical limits, much less anything as definitive as outright failure. That Vietnam was inarguably a defeat signifying unexpectedly confining limits—a great power unable to beat a bunch of peasants—was something that they and he refused to countenance.

So Reagan told Americans they didn’t have to. Declaring Vietnam a “noble cause” while insisting that if things hadn’t come out quite right it was because the troops weren’t allowed to win, he promised his countrymen a limitless future. “Top Gun” offered an action-hero depiction of what that meant—not the moral ambiguity of real life but good guys making short work of bad guys with triumphal music swelling over the closing credits.

Thanks to Reagan, it is always “Morning in America”—a claim to which each of his successors in turn has subscribed as a precondition for being elected president. That claim will echo far and wide as we enter the coming election cycle: you can bank on it.

So ironically, rather than calling into question the concept of American Exceptionalism, Vietnam became a vehicle for reaffirming it. “No more Vietnams” does not connote a determination to steer clear of unwinnable and unnecessary wars. Rather it signifies a collective resolve to avoid serious engagement with the past—to remember selectively, as befits the needs of a nation requiring constant reassurance that it is indeed indispensable.

Andrew J. Bacevich is a professor of history and international relations emeritus at Boston University’s Pardee School of Global Studies.