Secretary of Defense Pete Hegseth has scanned the horizon for threats, and sure enough, he has found a new group of dangerous adversaries: think-tanks, the organizations in the United States and allied nations that do policy research and advocate for various ideas. They must be stopped, according to a Defense Department announcement, because they promote “the evil of globalism, disdain for our great country, and hatred for the president of the United States.”This particular bit of McCarthyist harrumphing was the rationalization the Pentagon gave more than a week ago for pulling out of the Aspen Security Forum, a long-running annual conference routinely attended by business leaders, military officers, academics, policy analysts, foreign officials, and top government leaders from both parties, including many past secretaries of defense. For good measure, the Defense Department spokesperson Sean Parnell invoked the current holy words of the Hegseth Pentagon: The Aspen forum, he said, did not align with the department’s efforts to “increase the lethality of our war fighters, revitalize the warrior ethos and project peace through strength on the world stage.”The Aspen gathering is not exactly a secret nest of Communists. This year’s roster of speakers included former CIA Director Robert Gates, former Secretary of Defense Mark Esper—a Trump appointee—and a representative from Hungarian Prime Minister Viktor Orbán’s office, among many others. John Phelan, the current secretary of the Navy, and Admiral Samuel Paparo, the head of the U.S. Indo-Pacific Command, were set to attend as well.[Read: The Pentagon’s policy guy is all in on China]Nor is Hegseth content just to stop America’s intellectual enemies cold at the Rockies: The Pentagon last week suspended Defense Department participation in all such activities, functionally a blanket ban on any interaction with think tanks or other civilian institutions that hold conferences, convene panels, and invite speakers. The New York Times reported that the order to pull out of Aspen came from Hegseth personally. And as Politico first reported, the lager ban appears to extend “to gatherings hosted by nonprofit military associations, such as Sea Air Space, which is led by the Navy League, the military service’s largest veteran organization, and Modern Day Marine, a similar trade show for the Marine Corps.” The Pentagon also “specifically banned attendance at the Halifax International Security Forum, which takes place in Nova Scotia each winter and where the Pentagon chief is usually a top guest.”Take that, Canada.Right now, no one seems certain of how this new policy works. Hegseth appears to have suspended all such participation subject to additional review by the Pentagon’s public-affairs office and general counsel, so perhaps some defense officials could one day end up attending conferences after their requests have been vetted. Good luck with that, and best wishes to the first Pentagon employee who pops up out of their cubicle to request a pass to attend such meetings. At some point soon, this prohibition will almost certainly be lifted, but why did Hegseth’s Pentagon impose it in the first place?I am a former Defense Department employee who, over the course of my career, attended (and spoke at) dozens of conferences at various think tanks and other organizations, and I will make an educated guess based on experience: The main reasons are resentment, insecurity, and fear.The most ordinary reason, resentment, predates Hegseth. Government service is not exactly luxurious, and many trips are special perks that generate internal gripes about who gets to go, where they get to stay, and so on. (These trips are not exactly luxurious either, but in my government-service days, I learned that some people in the federal service chafe when other employees get free plane tickets to visit nice places.) It’s possible that someone who has never been invited to one of these things convinced Hegseth—who seems reluctant to attend such events himself—that these meetings are just boondoggles and that no one should go.Bureaucratic pettiness, however, isn’t enough of an explanation. One hazard for people like Hegseth and his lieutenants at a place like Aspen or the International Institute of Strategic Studies or the Halifax conference is that these are organizations full of exceptionally smart people, and even experienced and knowledgeable participants have to be sharp and prepared when they’re onstage and in group discussions. The chance of being outclassed, embarrassed, or just in over one’s head can be very high for unqualified people who have senior government jobs.Hegseth himself took a pass on the Munich Security Conference (usually a good venue for a new secretary of defense), and instead decided to show videos of himself working out with the troops. We can all admire Hegseth’s midlife devotion to staying fit and modeling a vigorous exercise regimen for the troops (who must exercise anyway, because they are military people and are ordered to it), but America and its allies would probably benefit more from a secretary with an extra pound here and there who could actually stand at a podium in Munich or London and explain the administration’s strategic vision and military plans. The overall prohibition on conferences provides Hegseth and his deputies (many of whom have no serious experience with defense issues) with an excuse for ducking out and avoiding making fools of themselves.But perhaps the most obvious and Trumpian reason for the Pentagon’s brainpower lockdown is fear. Officials in this administration know that the greatest risk to their careers has nothing to do with job performance; if incompetence were a cause for dismissal, Hegseth would have been gone months ago. The far greater danger comes from the chance of saying something in public that gets the speaker sideways with Trump and turns his baleful stare across the river to the Pentagon. “The Trump administration doesn’t like dissent, I think that’s pretty clear,” a Republican political strategist and previous Aspen attendee told The Hill last week. “And they don’t like dissenting views at conferences.”The problem for Trump officials is that “dissent” can mean almost anything, because the strategic direction of the United States depends on the president’s moods, his grievances, and his interactions with others, including foreign leaders. Everything can change in the space of a post on Truth Social. To step forward in a public venue and say anything of substance is a risk; the White House is an authoritarian bubble, and much like the Kremlin in the old Soviet Union, the man in charge can decide that what is policy today could be heresy tomorrow.[Read: When Pete Hegseth’s Pentagon tenure started going sideways]In the end, banning attendance at meetings where defense officials can exchange ideas with other intelligent people is—like so much else in this administration—a policy generated by pettiness and self-protection, a way to batten down the Pentagon’s hatches so that no one speaks out or screws up. If this directive stays in place for even a few years, however, it will damage relationships among the military, defense officials, business leaders, academics, and ordinary Americans.Public conferences are part of the American civil-military relationship. Sometimes, these are events such as Aspen, where senior officials present policies or engage their critics under a national spotlight; other gatherings at various nongovernmental organizations help citizens understand what, exactly, their government is doing. At academically oriented meetings, members of the defense community gather ideas, debate, discuss, and sometimes establish contacts for future research and exchanges. Retired Army Colonel Jeffrey McCausland, who served on the National Security Council staff and as the dean of the Army War College, told me that the Pentagon’s shortsightedness could prevent important civil-military exchanges about national defense, and he wonders how far such prohibitions will go: Might the new directive mean that the “guy who teaches history at West Point or a war college,” for example, “can’t go to a history conference and be a better history professor?”Maybe someone is mad that they didn’t get to go to Colorado or Canada; perhaps someone else is worried that accepting an invitation could be career suicide. Somehow, the Pentagon has managed to engage productively in such events for decades, under administrations of both parties. But Hegseth, after a string of embarrassments—McCausland points to the lingering “radioactivity” of Signalgate—has apparently chosen a safety-first approach. Unfortunately, the secretary still has to appear in public, and the chances of yet more stumbles from him and his team are high. But at least he’ll be able to reassure the American public that the upright employees of the Pentagon won’t be wined and dined by politically suspect eggheads.Besides, when people get together and start thinking, anything can happen. Better safe than sorry.