For a few hours, Pete Hegseth’s nomination as secretary of defense was the most disturbing act of Donald Trump’s presidential transition. Surely the Senate wouldn’t confirm an angry Fox News talking head with no serious managerial experience, best known for publicly defending war criminals, to run the largest department in the federal government. Then, in rapid succession, Trump announced appointments for Matt Gaetz, Tulsi Gabbard, and Robert F. Kennedy Jr. The appearance of these newer and even more aberrant characters, like a television show introducing a more villainous heel in its second season, muted the indignation over Hegseth.

Obscured in this flurry of shocking appointments is the fact that Hegseth’s drawbacks are not limited to his light résumé or to the sexual-assault allegation made against him. Inexperienced though he may be at managing bureaucracies, Hegseth has devoted a great deal of time to documenting his worldview, including three books published in the past four years. I spent the previous week reading them: The man who emerges from the page appears to have sunk deeply into conspiracy theories that are bizarre even by contemporary Republican standards but that have attracted strangely little attention. He considers himself to be at war with basically everybody to Trump’s left, and it is by no means clear that he means war metaphorically. He may be no less nutty than any of Trump’s more controversial nominees. And given the power he is likely to hold—command over 2 million American military personnel—he is almost certainly far more dangerous than any of them.

Hegseth began his involvement in conservative-movement politics as a Princeton undergraduate. He then joined the Army and quickly developed a profile, when not on active duty, as a budding Republican spokesperson. He testified against Elena Kagan’s appointment to the Supreme Court (on the grounds that, while dean of Harvard Law School, she had blocked military recruiters from campus in protest of Don’t Ask, Don’t Tell) and lobbied in favor of the Bush administration’s Iraq policy. As the Republican Party’s foreign-policy orientation changed radically under Donald Trump, Hegseth’s positions changed with it. But his devotion to the party remained constant. After stints running the advocacy groups Vets for Freedom and Concerned Veterans for America, and a failed Senate campaign, he finally settled at Fox News, where he joined a chorus in support of Trump.

Along the way, Hegseth has written five books. The first, extolling Teddy Roosevelt’s legacy, revolves around ideas that Hegseth has since renounced after converting to Trumpism. Another is simply a collection of war stories. The other three, all published in the past four years—American Crusade (2020), Battle for the American Mind (2022), and The War on Warriors (2024)—lay out his worldview in florid, explicit, and often terrifying detail.

A foundational tenet of Hegseth’s philosophy, apparently carrying over from his Roosevelt-worshipping era, is a belief in the traditional masculine virtues and the potential for war to inculcate them. Hegseth maintains that boys require discipline and must aspire to strength, resilience, and bravery. His preferred archetype for these virtues appears to be Pete Hegseth, whose manful exploits either on the basketball court (he played for Princeton) or the battlefield are featured in all three books.

[David A. Graham: The perverse logic of Trump’s nomination circus]

Hegseth complains that society no longer gives veterans like him their proper measure of deference. “Being a veteran no longer demands respect of the coastal elites or reverence from large swaths of the public,” he writes—an observation that will sound strange to anybody who has ever attended a football game or listened to a speech by a politician from either party. “In previous generations, men had to find ways to salvage their honor if they didn’t get to fight in a war.” (The single strongest piece of evidence for Hegseth’s thesis—the popularity of lifelong coastal elitist, proud war-avoider, and POW-mocker Donald Trump—goes unmentioned).

Hegseth’s demand for greater respect grows out of his belief that he personally succeeded in the face of forbidding odds. “I had been an underdog my whole life,” he writes. “I persisted. I worked my ass off.” But the woke military, he complains, doesn’t reward that kind of individual merit and grit. Instead, it has grown so obsessed with diversity that it promotes unqualified minorities and allows women in combat, reducing its effectiveness and alienating hard-working, meritorious soldiers such as, well, him. He also frets that the inclusion of women in combat erodes traditional gender norms. “How do you treat women in a combat situation,” he asks, “without eroding the basic instinct of civilization and the treatment of women in the society at large?”

(The treatment of women by Hegseth specifically happens to be the subject of a recently disclosed police report detailing an alleged sexual assault of a woman at a 2017 political conference. Hegseth denies the allegation and says that the encounter, which took place while he was transitioning between his second and third wives, was consensual. He paid the alleged victim an undisclosed sum in return for her signing a nondisclosure agreement.)

One episode looms especially large in Hegseth’s mind as the embodiment of the wokification of the military and its abandonment of traditional merit. In 2021, Hegseth, an active National Guard member, wished to join the Washington, D.C., unit protecting incoming President Joe Biden’s inauguration. The National Guard, however, excluded him from the detail because he was deemed a security risk on account of a bicep tattoo of the “Deus Vult” symbol—a reference to the Crusades that is popular with some far-right activists.

The logic of the snub was straightforward. Biden’s inauguration took place in the immediate aftermath of an insurrection attempt that had included many members of the armed forces, some operating within far-right networks. But to Hegseth—who protests that the Deus Vult tattoo is simply an expression of his Christian faith, not a white-nationalist symbol—the decision was an unforgivable personal affront.

He expresses indignation at the notion that he could even be suspected of harboring radical ideas. “I fought religious extremists for over twenty years in uniform,” he writes. “Then I was accused of being one.” This is not as paradoxical as Hegseth makes it sound. Many of the people most eager to fight against extremists of one religion are extremist adherents of another religion. An example of this would be the Crusades, an episode that Hegseth highlights in American Crusade as a model to emulate.

In any case, evidence of Hegseth’s extremism does not need to be deduced by interpreting his tattoos. The proof is lying in plain sight. In his three most recent books, Hegseth puts forward a wide range of familiarly misguided ideas: vaccines are “poisonous”; climate change is a hoax (they used to warn about global cooling, you know); George Floyd died of a drug overdose and was not murdered; the Holocaust was perpetrated by “German socialists.”

Where Hegseth’s thinking begins venturing into truly odd territory is his argument, developed in Battle for the American Mind, that the entire basic design of the public education system is the product of a century-long, totally successful communist plot. Hegseth is not just hyperventilating about the 1619 Project, Howard Zinn, or other left-wing fads, as conservatives often do. Instead he argues that the entire design of the U.S. education system is a Marxist scheme with roots going back to the founding of the republic. The deist heresies of Ben Franklin and Thomas Jefferson, he writes, laid the groundwork to implant communist thought into the school system. Then, “American Progressives in the late 1800s blended the idea of Marxist government with aspects from the Social Gospel and the belief in an American national destiny in order to make Marxism more palatable to Americans.”

The nefarious plan to turn America communist involves steps that appear anodyne to the untrained eye. “Yes, our modern social sciences—like ‘political science,’ previously known as ‘politics,’ and ‘social studies,’ previously known as individual disciplines like ‘history, economics, geography and philosophy’—are byproducts of Marxist philosophy,” he writes. “Let that sink in: the manner in which we study politics, history, and economics in American schools—public and private—today is the product of Marxists. That was always the plan, and it worked.” Hegseth will no longer sit back and allow communist indoctrination to sap and impurify our precious bodily fluids.

The Marxist conspiracy has also, according to Hegseth, begun creeping into the U.S. military, the institution he is now poised to run. His most recent book calls for a straightforward political purge of military brass who had the gall to obey Democratic administrations: “Fire any general who has carried water for Obama and Biden’s extraconstitutional and agenda-driven transformation of our military.” Trump appears to be thinking along similar lines. He is reportedly working on an executive order that will fast-track the removal of officers “lacking in requisite leadership qualities” and compiling a list of officers involved in the Afghanistan retreat, who will likewise be shoved out.

To what end? Trump has already signaled his interest in two revolutionary changes to the Defense Department’s orientation. One is to legalize war crimes, or at least cease enforcement of the rules of war. The president-elect has enthusiastically endorsed the use of illegal military methods and has pardoned American soldiers who committed atrocities against detainees and unarmed civilians, following a loud campaign by Hegseth on Fox News.

[Graeme Wood: War crimes are not difficult to discern]

In The War on Warriors, Hegseth makes plain that he considers the very idea of “rules of war” just more woke nonsense. “Modern war-fighters fight lawyers as much as we fight bad guys,” he writes. “Our enemies should get bullets, not attorneys.” He repeatedly disparages Army lawyers (“jagoffs”), even claiming that their pointless rules are “why America hasn’t won a war since World War II.” (Ideally, the secretary of defense would be familiar with historical episodes such as the Gulf War.)

Writing about his time guarding prisoners at Guantánamo Bay—where, as even the Bush administration eventually admitted, most detainees were innocent men swept up by American forces—Hegseth describes calls for due process as a stab-in-the-back against brave soldiers like himself. “The nation was dealing with legal issues (mostly led by weak-kneed, America-hating ACLU types) concerning enemy combatants, ‘international rights’ of illegal combatants, and the beginnings of extrajudicial drone attacks,” he writes. “Not to mention the debate about the ‘rights’ of assholes (I mean, ‘detainees’) at Gitmo.”

Trump’s second and even more disturbing interest in having a loyalist run the department is his enthusiasm for deploying troops to curtail and if necessary shoot domestic protesters. His first-term defense secretaries blanched at these demands. Hegseth displays every sign of sharing Trump’s impulses, but in a more theorized form.

The clearest throughline of all three books is the cross-application of Hegseth’s wartime mentality to his struggle against domestic opponents. American Crusade calls for the “categorical defeat of the Left,” with the goal of “utter annihilation,” without which “America cannot, and will not, survive.” Are the Crusades just a metaphor? Sort of, but not really: “Our American Crusade is not about literal swords, and our fight is not with guns. Yet.” (Emphasis—gulp—his).

Battle for the American Mind likewise imagines the struggle against the communist educational plot as a military problem: “We are pinned down, caught in an enemy near ambush. The enemy has the high ground, and is shooting from concealed and fortified positions.”

And The War on Warriors repeatedly urges Hegseth’s readers to treat the American left exactly like foreign combatants. Describing the military’s responsibility to the nation, he writes, “The expectation is that we will defend it against all enemies—both foreign and domestic. Not political opponents, but real enemies. (Yes, Marxists are our enemies.)” The Marxist exception swallows the “not political opponents” rule, because pretty much all of his political opponents turn out to be Marxists. These include, but are not limited to, diversity advocates (“They are Marxists … You know what they are? They’re traitors”), newspapers (“the communist Star Tribune”), and, as noted, almost anybody involved in public education.

Lest there be any ambiguity, Hegseth incessantly equates the left to wartime enemies. “They do not respect cease-fires, do not abide by the rules of warfare, and do not respect anything except total defeat of their enemy—and then total control,” he writes at one point. At another, he argues, “We should be in panic mode. Almost desperate. Willing to do anything to defeat the ‘fundamental transformation’ of the American military and end the war on our warriors.”

Hegseth’s idea of illegitimate behavior by the domestic enemy is quite expansive. Consider this passage, recalling his time advocating for the Iraq War: “While I debated these things in good faith, the Left mobilized. Electing Obama, railroading the military, pushing women in combat—readiness be damned. The left has never fought fair.” The most remarkable phrase there is “electing Obama.” Hegseth’s notion of unfair tactics used by the left includes not only enacting administrative policies that he disagrees with, but the basic act of voting for Democrats. The inability or unwillingness to distinguish between legitimate and illegitimate political opposition likely endeared Hegseth to Trump, who shares the trait.

A Defense Secretary with a tenuous grip on reality, who can’t differentiate foreign enemies from domestic political opponents, and who seems to exist in a state of permanent hysteria is a problem that the United States has never had to survive. The main question I was looking to answer when I started reading Hegseth’s collected works was whether he would follow a Trump command to shoot peaceful protesters. After having read them, I don’t think he would even wait for the order.

When I was taking German in college in the early years of this millennium, I once stumbled upon a word that appeared foreign even when translated into English: Diphtherie, or diphtheria. “What’s diphtheria?” I wondered, having never encountered a single soul afflicted by this disease.

Diphtheria, once known as the “strangling angel,” was a leading killer of children into the early 20th century. The bacterial infection destroys the lining of the throat, forming a layer of dead, leathery tissue that can cause death by suffocation. The disease left no corner of society untouched: Diphtheria killed Queen Victoria’s daughter, and the children of Presidents Lincoln, Garfield, and Cleveland. Parents used to speak of their first and second families, an elderly woman in Ottawa recalled, because diphtheria had swept through and all their children died.

Today, diphtheria has been so thoroughly forgotten that someone like me, born some 60 years after the invention of a diphtheria vaccine, might have no inkling of the fear it once inspired. If you have encountered diphtheria outside of the historical context, it’s likely because you have scrutinized a childhood immunization schedule: It is the “D” in the DTaP vaccine.

Vaccine breakthroughs over the past two centuries have cumulatively made the modern world a far more hospitable place to be born. For most of human history, half of all children died before reaching age 15; that number is down to just 4 percent worldwide, and far lower in developed countries, with vaccines one of the major drivers of improved life expectancy. “As a child,” the vaccine scientist Stanley Plotkin, now 92, told me, “I had several infectious diseases that almost killed me.” He ticked them off: pertussis, influenza, pneumococcal pneumonia—all of which children today are routinely vaccinated against.

But the success of vaccines has also allowed for a modern amnesia about the level of past human suffering. In a world where the ravages of polio or measles are remote, the risks of vaccines—whether imagined, or real but minute—are able to loom much larger in the minds of parents. This is the space exploited by Robert F. Kennedy Jr., one of the nation’s foremost anti-vaccine activists and now nominee for secretary of Health and Human Services. It is a stunning reversal of fortune for a man relegated to the fringes of the Democratic Party just last year. And it is also a reversal for Donald Trump, who might have flirted with anti-vaccine rhetoric in the past but also presided over a record-breaking race to create a COVID vaccine. Kennedy has promised that he would not yank vaccines off the market, but his nomination normalizes and emboldens the anti-vaccine movement. The danger now is that diseases confined to the past become diseases of the future.

Walt Orenstein trained as a pediatrician in the 1970s, when he often saw children with meningitis—a dangerous infection of membranes around the brain—that can be caused by a bacterium called Haemophilus influenzae type b or Hib. (Despite the name, it is not related to the influenza virus.) “I remember doing loads of spinal taps,” he told me, to diagnose the disease. The advent of a Hib vaccine in the 1980s virtually wiped these infections out; babies are now routinely vaccinated in the first 15 months of life. “It’s amazing there are people today calling themselves pediatricians who have never seen a case of Hib,” he says. He remembers rotavirus, too, back when it used to cause about half of all hospitalizations for diarrhea in kids under 5. “People used to say, ‘Don’t get the infant ward during diarrhea season,’” Orenstein told me. But in the 2000s, the introduction of rotavirus vaccines for babies six months and younger sharply curtailed hospitalizations.

To Orenstein, it is important that the current rotavirus vaccine has proved effective but also safe. An older rotavirus vaccine was taken off the market in 1999 when regulators learned that it gave babies an up to one-in-10,000 chance of developing a serious but usually treatable bowel obstruction called intussusception. The benefits arguably still outweighed the risks—about one in 50 babies infected with rotavirus need hospitalization—but the United States has a high bar for vaccine safety. Similarly, the U.S. switched from an oral polio vaccine containing live, weakened virus—which had a one in 2.4 million chance of causing paralysis—to a more expensive but safer shot made with inactivated viruses that cannot cause disease. No vaccine is perfect, says Gregory Poland, a vaccinologist and the president of the Atria Academy of Science & Medicine, who himself developed severe tinnitus after getting the COVID vaccine. “There will always be risks,” he told me, and he acknowledges the need to speak candidly about them. But vaccine recommendations are based on benefits that are “overwhelming” compared with their risks, he said.

The success of childhood vaccination has a perverse effect of making the benefits of these vaccines invisible. Let’s put it this way: If everyone around me is vaccinated for diphtheria but I am not, I still have virtually no chance of contracting it. There is simply no one to give it to me. This protection is also known as “herd immunity” or “community protection.” But that logic falls apart when vaccination rates slip, and the bubble of protective immunity dissolves. The impact won’t be immediate. “If we stopped vaccinating today, we wouldn’t get outbreaks tomorrow,” Orenstein said. In time, though, all-but-forgotten diseases could once again find a foothold, sickening those who chose not to be vaccinated but also those who could not be vaccinated, such as people with certain medical conditions and newborns too young for shots. In aggregate, individual decisions to refuse vaccines end up having far-reaching consequences.

Evolutionary biologists have argued that plague and pestilence rose in tandem with human civilization. Before humans built cities, back when we still lived in small bands of hunter-gatherers, a novel virus—say, from a bat—might tear through a group only to reach a dead end once everyone was immune or deceased. With no one else to infect, such a virus will burn itself out. Only when humans started clustering in large cities could certain viruses keep finding new susceptibles—babies or new migrants with no immunity, people with waning immunity—and smolder on and on and on. Infectious disease, you might then say, is a necessary condition of living in a society.

But human ingenuity has handed us a cheat code: Vaccines now allow us to enjoy the benefits of fellow humanity while preventing the constant exchange of deadly pathogens. And vaccines can, through the power of herd immunity, protect even those who are too young or too sick to be effectively vaccinated themselves. When we get vaccinated, or don’t, our decisions ricochet through the lives of others. Vaccines make us responsible for more than ourselves. And is that not what it means to live in a society?