SECRETARY OF DEFENSE PETE HEGSETH said Sunday that the DoD “does not do climate change crap,” implying the department should focus solely on training and war-fighting, and anything else is a distraction. While it may be a pithy soundbite, it reflects a dangerous blind spot—and contradicts a fundamental strategic principle.

Many people in the military, possibly even Hegseth himself, are familiar with Sun Tzu’s famous statement: “If you know the enemy and know yourself, your victory will not stand in doubt.” Many fewer remember the following lines: “if you know Heaven and know Earth, you may make your victory complete.” Perhaps Sun Tzu was speaking metaphorically, but the rest of The Art of War is supremely practical, and any good soldier knows that terrain and weather—and, yes, climate—can be key allies or stern enemies.

As a combat commander in Iraq during the 2007 “surge,” I experienced firsthand how climatic conditions can disrupt operations. I had planned a ten-day operation involving a U.S. task force, and special operations forces, and five Iraqi Army divisions in northern Iraq. As we were about to kick off, we were hit by severe dust and sandstorms—“shamals” and “haboobs”—intensified by prolonged drought. (It was just about the same time that the National Intelligence Council was working on its first ever report on climate change, which found a likelihood of “increase of heat waves and droughts (both in frequency and intensity).” These storms canceled air operations, grounded reconnaissance platforms, blinded intelligence collectors, delayed maneuvers, and severely degraded communications. It became clear to everyone in our command: climate change wasn’t background noise—it was an operational variable. The weather forced us to delay a major tactical operation against our enemy for weeks; the climate made it more likely that more such operations would be delayed or canceled in the future.

That’s just one example—there are plenty of others from every service, domain, and combatant command to illustrate why climate change is a strategic issue that demands the attention of the secretary of defense. Sea level rise, storm surges, and extreme weather events increasingly threaten mission-critical infrastructure. Naval Station Norfolk—the world’s largest naval base—now experiences frequent tidal flooding that disrupts operations and damages infrastructure. Other key installations like Pearl Harbor, San Diego, and Key West face similar vulnerabilities. In 2018, Tyndall Air Force Base suffered $4 billion in hurricane-related damage.

Melting Arctic Sea ice is opening new transit routes and fueling geopolitical competition. Russia has militarized its Arctic coastline, and China has declared itself a “near-Arctic power”—a term it invented, since it doesn’t actually border the Arctic. During my time as Commander of U.S. Army Europe, our NATO allies—especially Canada, Norway, as well as Sweden and Finland, which have since joined the alliance— had expanded cold-weather training, exercises, and operations in their armies and navies. The Arctic has warmed nearly four times as fast as the rest of the planet in recent decades, and as it gets warmer, it becomes a more viable theater of military competition. Not surprisingly, our allies have modernized their Arctic fleets and the ability of their armies to thrive in cold-weather environments. Mirroring their efforts, our Marines and Army incorporated similar exercises.The president himself, at least momentarily, seemed to recognize the effects of climate change when he made the surprise—and apparently misleading—announcement of the purchase of “about 40 big icebreakers.” At the same time, the Defense Department canceled a training exercise in Sweden. It’s challenging to determine the logic.

Climate change is driving instability across the globe. When crops fail or water runs dry, populations move, and crises follow. Climate-driven migration is already destabilizing regions across Central America, the Middle East, Africa, and South Asia. Commanders at Southern Command and Africa Command have repeatedly testified that environmental degradation is a primary driver of insecurity. The 2024 Annual Threat Assessment by the Office of the Director of National Intelligence found that “the accelerating effects of climate change are placing more of the world’s population, particularly in low- and middle-income countries, at greater risk from extreme weather, food and water insecurity, and humanitarian disasters, fueling migration flows and increasing the risks of future pandemics as pathogens exploit the changing environment.” The secretary of defense normally listens to combatant commanders for input into the National Defense Strategy, but Hegseth seems to be precluding one of the major threats.

Climate shocks also create domestic demands on U.S. forces. The DoD is increasingly deploying National Guard and active-duty units to the southern border in response to political and climate-driven migration. Those missions will continue to compete for manpower and resources with military support to disaster relief operations. National Guard troops are increasingly asked to respond to out-of-control wildfires, severe hurricanes, and repeated once-in-a-century floods—missions that strain personnel and divert readiness. In 2023 alone, U.S. troops responded to record-breaking floods in Vermont, massive wildfires in California and Hawaii, and major hurricanes in the east and southeast. The disaster-related demands increased in 2024 and are expected to grow even larger in the future.

Facts matter. Running the Department of Defense requires strategic foresight based on critical analysis and force requirement assessments, not uninformed ideology or political soundbites for the base. Sun Tzu’s wisdom holds: We must know the enemy, know ourselves, and know the heaven and the earth. Today’s terrain includes rising seas, melting ice, extreme weather, shifting populations, and new demands on the force. Climate change is not a distant future threat—it’s shaping tomorrow’s battlefields, on land, sea and in the air, right now. To ignore it—or worse, dismiss it as “crap”—is not conservatism. It’s strategic malpractice.

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