On any given day last summer, the smoke-choked skies over Missoula, Montana, swarmed with an average of twenty-eight helicopters and eighteen fixed-wing craft, a blitz waged against Lolo Peak, Rice Ridge, and ninety-six other wildfires in the Lolo National Forest. On the ground, forty or fifty twenty-person handcrews were deployed, alongside hundreds of fire engines and bulldozers. In the battle against Rice Ridge alone, the Air Force, handcrews, loggers, dozers, parachutists, flacks, forecasters, and cooks amounted to some nine hundred people.

Rice Ridge was what is known as a mega-fire, a recently coined term for blazes that cover more than 100,000 acres. The West has always known forest fires, of course, but for much of the past century, they rarely got any bigger than 10,000 acres. No more. In 1988, a 250,000-acre anomaly, Canyon Creek, burned for months, roaring across a forty-mile stretch of Montana’s Bob Marshall Wilderness in a single night. A few decades on, that anomaly is becoming the norm. Rice Ridge, for its part, swept through 160,000 acres.

At this scale, the firefighting operation is run by an incident management team, a group of about thirty specialists drawn from a mix of state and federal agencies and trained in fields ranging from aviation to weather forecasting and accounting to public information. The management teams are ranked according to experience and ability, from type 3 (the least skilled) to type 1 (the most). The fiercest fires are assigned to type 1s. Teams take the name of their incident commander, the field general, and some of those names become recognizable, even illustrious, in the wildfire-fighting community. One such name is that of Greg Poncin, who is to fire commanders what Wyatt Earp was to federal marshals.

The pinhal interior, a wooded region of hills and narrow hollows in rural central Portugal, used to be farmland. Well into the latter half of the past century, the fields were worked by peasants from the old stone villages. Portugal was poor and isolated, and the pinhal interior particularly so; when they could, the peasants left. There is electricity and running water now, but most of the people have gone. The fields have been taken over by trees. Each year the forest encroaches farther, and each year the villages grow more lonely. There are remnants of the earlier life, though, and amid the trees the holdouts of the older generations still work a few small fields. The pinhal interior cannot yet be called wilderness, then, and that, in large part, is why it burns.

Thousands of fires burn in the region each summer, almost all of them started not by lightning or some other natural spark but by the remaining Portuguese. (The great majority of the blazes are started unintentionally, though not all.) The pinhal interior—the name means “interior pine forest,” though today there is at least as much eucalyptus as pine—stretches along a sort of climate border between the semiarid Iberian interior and the wet influence of the Atlantic; vegetation grows exceptionally well there, and in the summers fire conditions are ideal. Still, most of the burns are quickly contained, and although they have grown larger in recent years, residents have learned to pay them little mind. The creeping fire that began in the dry duff and twigs of an oak grove on June 17 of last year, in the district of Pe­drógão Grande, therefore occasioned no panic.

A local woman, Dora da Silva Co­sta, drove past the blaze in the midafternoon, by which time it had entered a stand of pines. Firefighters were on hand. “There were no people in the streets,” Costa told me. “It was just another fire.” She continued on her way. It was a Saturday, and she had brought her two young sons to visit their older cousin in Vila Facaia, the village of small farms in which she’d been raised.

On a blistering morning in July 2017, Ghazi Luaibi rose before dawn and set out in a worn black sedan from his home in Zubair, a town of concrete low-rises in southern Iraq. He drove for a while along sandy roads strewn with plastic bags. On the horizon, he could see gas flares from the oil refineries, pillars of amber flame rising into the sky. As he approached Basra, the largest city in the province, desert scrub gave way to empty apartment blocks and rows of withered palms. Though the sun had barely risen, the temperature was already nearing 100 degrees Fahrenheit. The previous year, Basra had registered one of the highest temperatures ever reliably recorded on earth: about 129 degrees, hot enough to cause birds to drop from the sky.

Ghazi, a sixty-two-year-old with stooped shoulders, an ash-gray beard, and lively brown eyes, would have preferred to stay home and wait out the heat. But he hadn’t had much of a choice. He was the president of the local council of Mandaeans, members of a gnostic religion that appeared in Mesopotamia in the early centuries ad. Today marked the beginning of their new year, and Ghazi, who was born into the Mandaean priestly class, was responsible for making sure everything went smoothly: he needed to find a tent to shield worshippers from the sun and, most importantly, a location near flowing water where they could carry out the ceremony.

Mandaean holidays are celebrated with a mass baptism, a ritual that is deeply rooted in their scripture and theology. Mandaeans follow the teachings of Yahia Yuhana, known to Christians as John the Baptist. Water is central to their religion. They believe that all life originates in the World of Light, a spiritual realm that is the starting point for a great river known as Yardana, or Jordan. Outside the World of Light lie the lifeless, stagnant waters of the World of Darkness. According to one version of the Mandaean creation myth, a demiurge named Ptahil set out to shape a new world from the World of Darkness, which became the material world we inhabit today. Once the world was complete, Ptahil sculpted Adam, the first man, from the same dark waters as the earth, but his soul came from the World of Light. In Mandaean scripture, rivers are manifestations of the World of Light, coursing from the heavenly Jordan to the earth to purify it. To be baptized is to be immersed in this divine realm.

Serving as a US Air Force launch control officer for intercontinental missiles in the early Seventies, First Lieutenant Bruce Blair figured out how to start a nuclear war and kill a few hundred million people. His unit, stationed in the vast missile fields at Malmstrom Air Force Base, in Montana, oversaw one of four squadrons of Minuteman II ­ICBMs, each missile topped by a W56 thermonuclear warhead with an explosive force of 1.2 megatons—eighty times that of the bomb that destroyed Hiroshima. In theory, the missiles could be fired only by order of the president of the United States, and required mutual cooperation by the two men on duty in each of the launch control centers, of which there were five for each squadron.

In fact, as Blair recounted to me recently, the system could be bypassed with remarkable ease. Safeguards made it difficult, though not impossible, for a two-man crew (of either captains or lieutenants, some straight out of college) in a single launch control center to fire a missile. But, said Blair, “it took only a small conspiracy”—of two people in two separate control centers—to launch the entire squadron of fifty missiles, “sixty megatons targeted at the Soviet Union, China, and North Korea.” (The scheme would first necessitate the “disabling” of the conspirators’ silo crewmates, unless, of course, they, too, were complicit in the operation.) Working in conjunction, the plotters could “jury-rig the system” to send a “vote” by turning keys in their separate launch centers. The three other launch centers might see what was happening, but they would not be able to override the two votes, and the missiles would begin their firing sequence. Even more alarmingly, Blair discovered that if one of the plotters was posted at the particular launch control center in overall command of the squadron, they could together format and transmit a “valid and authentic launch order” for general nuclear war that would immediately launch the entire US strategic nuclear missile force, including a thousand Minuteman and fifty-four Titan missiles, without the possibility of recall. As he put it, “that would get everyone’s attention, for sure.” A more pacifically inclined conspiracy, on the other hand, could effectively disarm the strategic force by formatting and transmitting messages invalidating the presidential launch codes.

When he quit the Air Force in 1974, Blair was haunted by the power that had been within his grasp, andhe resolved to do something about it. But when he started lobbying his former superiors, he was met with indifference and even active hostility. “I got in a fair scrap with the Air Force over it,” he recalled. As Blair well knew, there was supposed to be a system already in place to prevent that type of unilateral launch. The civilian leadership in the Pentagon took comfort in this, not knowing that the Strategic Air Command, which then controlled the Air Force’s nuclear weapons, had quietly neutralized it.

This reluctance to implement an obviously desirable precaution might seem extraordinary, but it is explicable in light of the dominant theme in the military’s nuclear weapons culture: the strategy known as “launch under attack.” Theoretically, the president has the option of waiting through an attack before deciding how to respond. But in practice, the system of command and control has been organized so as to leave a president facing reports of incoming missiles with little option but to launch. In the words of Lee Butler, who commanded all US nuclear forces at the end of the Cold War, the system the military designed was “structured to drive the president invariably toward a decision to launch under attack” if he or she believes there is “incontrovertible proof that warheads actually are on the way.” Ensuring that all missiles and bombers would be en route before any enemy missiles actually landed meant that most of the targets in the strategic nuclear war plan would be destroyed—thereby justifying the purchase and deployment of the massive force required to execute such a strike.

Among students of nuclear command and control, this practice of precluding all options but the desired one is known as “jamming” the president. Blair’s irksome protests threatened to slow this process. When his pleas drew rejection from inside the system, he turned to Congress. Eventually the Air Force agreed to begin using “unlock codes”—codes transmitted at the time of the launch order by higher authority without which the crews could not fire—on the weapons in 1977. (Even then, the Navy held off safeguarding its submarine-launched nuclear missiles in this way for another twenty years.)

Following this small victory, Blair continued to probe the baroque architecture of nuclear command and control, and its extreme vulnerability to lethal mishap. In the early Eighties, while working with a top-secret clearance for the Office of Technology Assessment, he prepared a detailed report on such shortcomings. The Pentagon promptly classified it as SIOP-ESI—a level higher than top secret. (SIOP stands for Single Integrated Operational Plan, the US plan for conducting a nuclear war. ESI stands for Extremely Sensitive Information.) Hidden away in the Pentagon, the report was withheld from both relevant senior civilian officials and the very congressional committees that had commissioned it in the first place.

From positions in Washington’s national security think tanks, including the Brookings Institution, Blair used his expertise and scholarly approach to gain access to knowledgeable insiders at the highest ranks, even in Moscow. On visits to the Russian capital during the halcyon years between the Cold War’s end and the renewal of tensions in the twenty-first century, he learned that the Soviet Union had actually developed a “dead hand” in ultimate control of their strategic nuclear arsenal. If sensors detected signs of an enemy nuclear attack, the USSR’s entire missile force would immediately launch with a minimum of human intervention—in effect, the doomsday weapon that ends the world in Dr. Strangelove.

Needless to say, this was a tightly held arrangement, known only to a select few in Moscow. Similarly chilling secrets, Blair continued to learn, lurked in the bowels of the US system, often unknown to the civilian leadership that supposedly directed it. In 1998, for example, on a visit to the headquarters of Strategic Command (­STRATCOM), the force controlling all US strategic nuclear weapons, at Offutt Air Force Base, near Omaha, Nebraska, he discovered that the ­­­STRATCOM targeting staff had unilaterally chosen to interpret a presidential order on nuclear targeting in such a way as to reinsert China into the ­SIOP, from which it had been removed in 1982, thereby provisionally consigning a billion Chinese to nuclear immolation. Shortly thereafter, he informed a senior White House official, whose reaction Blair recalled as “surprised” and “befuddled.”

In 2006, Blair founded Global Zero, an organization dedicated to ridding the world of nuclear weapons, with an immediate goal of ending the policy of launch under attack. By that time, the Cold War that had generated the ­SIOP and all those nuclear weapons had long since come to an end. As a result, part of the nuclear war machine had been dismantled—warhead numbers were reduced, bombers taken off alert, weapons withdrawn from Europe. But at its heart, the system continued unchanged, officially ever alert and smooth running, poised to dispatch hundreds of precisely targeted weapons, but only on receipt of an order from the commander in chief.