Deployed to the Houston area to assist in Hurricane Harvey relief efforts, U.S. military forces hadn’t even completed their assignments when they were hurriedly dispatched to Florida, Puerto Rico, and the U.S. Virgin Islands to face Irma, the fiercest hurricane ever recorded in the Atlantic Ocean. Florida Governor Rick Scott, who had sent members of the state National Guard to devastated Houston, anxiously recalled them while putting in place emergency measures for his own state. A small flotilla of naval vessels, originally sent to waters off Texas, was similarly redirected to the Caribbean, while specialized combat units drawn from as far afield as Colorado, Illinois, and Rhode Island were rushed to Puerto Rico and the Virgin Islands. Meanwhile, members of the California National Guard were being mobilizedto fight wildfires raging across that state (as across much of the West) during its hottest summer on record.

Think of this as the new face of homeland security: containing the damage to America’s seacoasts, forests, and other vulnerable areas caused by extreme weather events made all the more frequent and destructive thanks to climate change. This is a “war” that won’t have a name — not yet, not in the Trump era, but it will be no less real for that. “The firepower of the federal government” was being trained on Harvey, as William Brock Long, administrator of the Federal Emergency Management Agency (FEMA), put itin a blunt expression of this warlike approach. But don’t expect any of the military officials involved in such efforts to identify climate change as the source of their new strategic orientation, not while Commander in Chief Donald Trump sits in the Oval Office refusing to acknowledge the reality of global warming or its role in heightening the intensity of major storms; not while he continues to stock his administration, top to bottom, with climate-change deniers.

Until Trump moved into the White House, however, senior military officers in the Pentagon were speaking openly of the threats posed to American security by climate change and how that phenomenon might alter the very nature of their work. Though mum’s the word today, since the early years of this century military officials have regularly focused on and discussed such matters, issuing striking warnings about an impending increase in extreme weather events — hurricanes, incessant rainfalls, protracted heat waves, and droughts — and ways in which that would mean an ever-expanding domestic role for the military in both disaster response and planning for an extreme future.

That future, of course, is now. Like other well-informed people, senior military officials are perfectly aware that it’s difficult to attribute any given storm, Harvey and Irma included, to human-caused climate change with 100% confidence. But they also know that hurricanes draw their fierce energy from the heat of tropical waters, and that global warming is raising the temperatures of those waters. It’s making storms like Harvey and Irma, when they do occur, ever more powerful and destructive. “As greenhouse gas emissions increase, sea levels are rising, average global temperatures increasing, and severe weather patterns are accelerating,” the Department of Defense (DoD) bluntly explained in the Quadrennial Defense Review, a 2014 synopsis of defense policy. This, it added, “may increase the frequency, scale, and complexity of future missions, including defense support to civil authorities” — just the sort of crisis we’ve been witnessing over these last weeks.

As this statement suggests, any increase in climate-related extreme events striking U.S. territory will inevitably lead to a commensurate rise in American military support for civilian agencies, diverting key assets — troops and equipment — from elsewhere. While the Pentagon can certainly devote substantial capabilities to a small number of short-term emergencies, the multiplication and prolongation of such events, now clearly beginning to occur, will require a substantial commitment of forces, which, in time, will mean a major reorientation of U.S. security policy for the climate change era. This may not be something the White House is prepared to do today, but it may soon find itself with little choice, especially since it seems so intent on crippling all civilian governmental efforts related to climate change.

Mobilizing for Harvey and Irma

When it came to emergency operations in Texas and Florida, the media understandably put its spotlight on moving tales of rescue efforts by ordinary folks. As a result, the military’s role in these operations was easy to miss, but it took place on a massive scale. Every branch of the armed services — the Army, Navy, Air Force, Marine Corps, and Coast Guard — deployed significant contingents to the Houston area, in some cases sending along the sort of specialized equipment normally used in major combat operations. The combined response represented an extraordinary commitment of military assets to that desperate, massively flooded region: tens of thousands of National Guard and active-duty troops, thousands of Humvees and other military vehicles, hundreds of helicopters, dozens of cargo planes, and an assortment of naval vessels. And just as operations in Texas began to wind down, the Pentagon commenced a similarly vast mobilization for Hurricane Irma.

The military’s response to Harvey began with front-line troops: the National Guard, the U.S. Coast Guard, and units of the U.S. Northern Command(USNORTHCOM), the joint-service force responsible for homeland defense. Texas Governor Greg Abbott mobilized the entire Texas National Guard, about 10,000 strong, and guard contingents were deployed from other states as well. The Texas Guard came equipped with its own complement ofhelicopters, Humvees, and other all-terrain vehicles; the Coast Guard supplied 46 helicopters and dozens of shallow-water vessels, while USNORTHCOM provided 87 helicopters, four C-130 Hercules cargo aircraft, and 100 high-water vehicles.

Still more aircraft were provided by the Air Force, including seven C-17 cargo planes and, in a highly unusual move, an E-3A Sentry airborne warning and control system, or AWACS. This super-sophisticated aircraft was originally designed to oversee air combat operations in Europe in the event of an all-out war with the Soviet Union. Instead, this particular AWACS conducted air traffic control and surveillance around Houston, gathering data on flooded areas, and providing “situational awareness” to military units involved in the relief operation.

For its part, the Navy deployed two major surface vessels, the USS Kearsarge, an amphibious assault ship, and the USS Oak Hill, a dock landing ship. “These ships,” the Navy reported, “are capable of providing medical support, maritime civil affairs, maritime security, expeditionary logistic support, [and] medium and heavy lift air support.” Accompanying them were several hundred Marines from the 26th Marine Expeditionary Unit based at Camp Lejeune, North Carolina, along with their amphibious assault vehicles and a dozen or so helicopters and MV-22 Osprey tilt-rotor aircraft.When Irma struck, the Pentagon ordered a similar mobilization of troops and equipment. The Kearsarge and the Oak Hill, with their embarked Marines and helicopters, were redirected from Houston to waters off Puerto Rico and the Virgin Islands. At the same time, the Navy dispatched a much larger flotilla, including the USS Abraham Lincoln (the aircraft carrier on which President George W. Bush had his infamous “mission accomplished” moment), the missile destroyer USS Farragut, the amphibious assault ship USS Iwo Jima, and the amphibious transport dock USS New York. Instead of its usual complement of fighter jets, the Abraham Lincoln set sail from its base in Norfolk, Virginia, with heavy-lift helicopters; the Iwo Jima and New York also carried a range of helicopters for relief operations. Another amphibious vessel, the USS Wasp, was already off the Virgin Islands, providing supplies and evacuating those in need of emergency medical care.

This represents the sort of mobilization you would expect for a small war and is characteristic of how, in the past, the U.S. military has responded to major domestic disasters like hurricanes Katrina (2003) and Sandy (2012). Such events were once rarities and so weren’t viewed as major impediments to the carrying out of the military’s “normal” function: fighting the nation’s foreign wars. However, thanks to the way climate change is intensifying the weather, disasters of this magnitude are starting to occur more frequently and on an ever-larger scale. As a result, the previously peripheral mission of disaster relief is threatening to become a primary one for an already overstretched Pentagon and, as top military officials are aware, the future only holds promise of far more of the same. Think of this as the new face of “war,” American-style.

Redefining Homeland Security

Even if no one else in Donald Trump’s Washington is ready or willing to deal with climate change, the U.S. military will be. It’s already long been preparing in its own fashion to take a pivotal role in responding to a world of recurring natural disasters. This, in turn, will mean that in the coming years climate change will increasingly dominate the domestic national security agenda (whether the Trump administration and those that follow like it, or even admit it) and such domestic emergencies will undoubtedly be militarized. In the process, the very concept of “homeland security” is destined to change.

When the Department of Homeland Security (DHS) was established in November 2002 in the wake of the 9/11 terror attacks, its principal missionsincluded preventing further terrorist assaults on the country as well as dealing with drug smuggling, illegal immigration, and other similar issues. Climate change never entered the equation. Even though FEMA and the Coast Guard, major components of the DHS, have found themselves dealing with its increasingly disastrous effects, the department’s focus on immigration and terrorism has only intensified in the Trump era. The president has ensured that this myopic outlook would reign supreme by, among other things, calling for a sharp increase in the number of Border Patrol agents (and greater infusions of funding for border control issues), while working to slash the Coast Guard’s budget.

He has also, of course, ensured that all parts of the government other than the military that might in any way deal with climate change were staffed and run by climate-change deniers. Only at the Department of Defense do senior officials still describe climate change in a more realistic fashion, as an observable reality that will pose new dangers to America’s security and create new operational nightmares.

“Speaking as a soldier,” said former Army Chief of Staff General Gordon Sullivan back in 2007, “we never have 100 percent certainty. If you wait until you have 100 percent certainty, something bad is going to happen on the battlefield.” The same, he continued, was true regarding climate change. “If we keep on with business as usual, we will reach a point where some of the worst effects are inevitable.”

General Gordon’s comments were incorporated into a highly influential report that year on “National Security and the Threat of Climate Change,” released by the CNA Corporation (formerly the Center for Naval Analyses), a federally-funded research center that aids the Navy and Marine Corps. That report focused with particular concern on the risk of an increase in overseas conflicts from the impact of climate change, particularly if prolonged droughts and growing food scarcity inflame existing ethnic and religious schisms in a range of poor countries (mainly in Africa and the Greater Middle East). “The U.S. may be drawn more frequently into these situations, either alone or with allies, to help provide stability before conditions worsen and are exploited by extremists,” the report warned.

The same climate effects that could trigger a more embattled world would also, military analysts came to believe, produce increased risk for the United States itself and so generate a greater need for Pentagon involvement at home. “Extreme weather events and natural disasters, as the U.S. experienced with Hurricane Katrina, may lead to increased missions for a number of U.S. agencies, including state and local governments, the Department of Homeland Security, and our already stretched military,” that CNA report noted a decade ago. In a prescient comment, it also warned that this could lead to clashing strategic priorities. “If the frequency of natural disasters increases with climate change, future military and political leaders may face hard choices about where and when to engage.”

With this in mind, a group of officers — active duty as well as retired — endeavored to persuade top officials to make climate change a central focus of strategic planning. (Their collective efforts can be sampled at the website maintained by the Center for Climate and Security, an advocacy group former officers established to promote awareness of the issue.) These efforts achieved a major breakthrough in 2014, when the Pentagon released a Climate Change Adaptation Roadmap, a blueprint for Pentagon-wide remedial action in a warming world. Such an effort was needed, Secretary of Defense Chuck Hagel explained in his foreword, because climate change was sure to generate more conflict abroad and more emergencies at home. “The military could be called upon more often to support civil authorities, and provide humanitarian assistance and disaster relief in the face of more frequent and more intense natural disasters.” As a consequence, the DoD and its component organizations must begin “integrating climate change considerations into our plans, operations, and training.”

For a time, the armed forces embraced Hagel’s instructions, taking steps to reduce their carbon emissions and better prepare for just such a future. The various regional combatant commands like NORTHCOM and the U.S. Southern Command (SOUTHCOM), which covers Latin America and the Caribbean, responded with increased training and other preparations for extreme storm events and for sea-level rise in their areas of responsibility, a change reflected in a 2015 DoD report to Congress, “National Security Implications of Climate-Related Risks and a Changing Climate.”

In the past, such efforts, only beginning, were never allowed to distract the services from their main presumed function: contesting America’s foreign adversaries. Now, as with Harvey and Irma, the military’s domestic responsibilities are on the rise just as the president is assigning them yet more (or more intensified) missions in the never-ending war on terror, including a stepped-up presence in Afghanistan as well as in Iraq and Syria, more intense air campaigns across the Greater Middle East, and a heightened pace of military maneuvers near North Korea. As shown by a series of deadly collisions involving Navy vessels in the Pacific, this higher tempo of operations has already stretched the military to or even beyond its limits in various conflicts it has proven incapable either of winning or ending. The result: overworked crews and overstretched resources. With the massive response to Harvey and Irma, it is being pushed yet further.

In short, as the planet continues to heat up, the armed forces and the nation at large face an existential crisis. On the one hand, President Trump and his generals, including Secretary of Defense Mattis, are once again fully focused on the increased use of military force (and the threat of more of the same) abroad. This includes not only the wars against the Taliban, ISIS, al-Qaeda, and their numerous spin-offs, but also preparations for possible military strikes on North Korea and perhaps even, at some future date, on Chinese installations in the South China Sea.

As global warming intensifies, instability and chaos, including massive flows of refugees, will only grow, undoubtedly inviting yet more military interventions abroad. Meanwhile, climate change will increase chaos and devastation at home and there, too, it seems that Washington will often see the military as America’s sole reliable response mechanism. As a result, decisions will have to be made about ending American conflicts abroad and refocusing domestically or that overstretched military will simply swallow even more of the government’s dollars and gain yet more power in Washington. And yet, whatever else the armed forces might (or might not) be capable of, they are not capable of defeating climate change, which, at its essence, is anything but a military problem. While there are potential solutions to it, those, too, are in no way military.

Despite their reluctance to speak publicly about such environmental matters right now, top officials in the Pentagon are painfully aware of the problem at hand. They know that global warming, as it progresses, will generate new challenges at home and abroad, potentially stretching their capabilities to the breaking point and leaving this country ever more exposed to the ravages of climate change without offering any solutions to the problem. As a result, the generals face a fundamental choice. They can continue to self-censor their sophisticated analysis of climate change and its likely effects, and so remain complicit with the administration’s headlong rush into national catastrophe, or they can speak out forcefully on its threat to homeland security, and the resulting need for a new, largely non-military strategic posture that puts climate action at the top of the nation’s priorities.