And there they function to make some kinds of ideas seem self-evidently “realist,” hard-nosed and rational, and others patently inadmissible, self-evidently inappropriate. (One white male physicist told me that he and colleagues were once modeling a limited nuclear attack when he suddenly voiced dismay that they were talking so casually about “only 30 million” immediate deaths. “It was awful — I felt like a woman,” he said.)

In other words, embedded ideas about gender in nuclear strategic discourse go beyond questions of whether a button is more than just a button. They act as a deterrent to more holistic, and therefore truly realistic, thinking about nuclear weapons and the holocaust that would result from their use.

Mainstream national security analysts have been reluctant to think seriously — or at all — about the ways that ideas about gender shape national security. So if Mr. Trump’s disparagement of Mr. Kim’s manhood somehow does not wind up bringing us yet closer to war with North Korea, then perhaps he has in one sense done us a favor. He has made it glaringly evident that while the literal button or penis size of Mr. Trump or Mr. Kim matters not at all, their need for the world to believe that they are manly men does.

What we now need to remember is that Mr. Trump is, in this respect, not an exception. Yes, the fear of being perceived as unmanly may be closer to the surface in Mr. Trump. And it may drive his statements and actions in ways less leavened by cognitive capacity and attention span, or by empathy and the ability to imagine the impact of one’s actions on others, or by intelligence or prudence.

But this is not about individual men or women. Ideas about masculinity and femininity already distort the ways we think about international politics and national security. And they matter. They mattered before Mr. Trump, they matter now, and they will matter after Mr. Trump, if he is somehow kept under control and there is an after. Most national security analysts, from the academy to the mass media to the executive branch, have ignored this reality for too long, to all of our peril.