President-elect Donald Trump. (Jabin Botsford /The Washington Post)

Richard H. Kohn is an emeritus professor of history and peace, war and defense at the University of North Carolina at Chapel Hill.

Dear Republican national security expert:

Like dozens of other prominent GOP national security leaders, you may have publicly opposed Donald Trump’s presidential campaign in harsh terms. (Or perhaps you found him appalling but kept your views to yourself.) Now that he will be moving into the White House, however, you must serve in a Trump administration if given the opportunity.

A president as seriously deficient in knowledge, experience and temperament as Trump is going to need a lot of help, and he will need it from the A-Team. Most national political figures have established ideas about policy and also know many individuals who are qualified and prepared to people their administrations. Given his demagoguery, inconsistency and changeability, Trump lacks a fixed agenda. He’s all style, no substance — a tabula rasa.

With your experience and professional network, you could help Trump find the dozens of appointees necessary to direct the foreign policy, national defense, intelligence, homeland security and other agencies that defend the country. You can suggest generals and admirals for the different commands and let Trump know whose advice to heed in the many ticklish (and dangerous) situations sure to arise during his term. You can warn him when a given comment or idea will tempt or deter an adversary, reassure or unhinge an ally, strengthen or weaken our war-making capacity. You will know how to craft the short memos needed to get his attention and which perspectives will need to be added to the policy discussions that will be ongoing in his administration. You might even prevent a financial as well as a national security crisis.

I know you worry deeply about working for a man you dislike and distrust. Remember, however, that you would be serving the American people and the country. It can be done.

To succeed, you will have to be prepared to speak truth to power, and then to be ignored, overruled, dissed and otherwise embarrassed. The people in charge may not be principled or capable and, including in Trump’s case, perhaps even disparaging of those around them and working for them. In other words, the gig may test your capacity for abuse. Be prepared to resign or otherwise walk off the job after careful calculation of the pros and cons of helping the country vs. going home to lick one’s wounds. The only people who can’t resign in the national security community are the most senior military leaders, because to do so would violate their core professional obligations, akin to an emergency-room doctor walking away from a patient in need.

You will also have to inquire carefully about the conditions of service. Trump is known for requiring nondisclosure agreements from his employees. You may have to measure a promise to go home in silence against what may be a need to alert the country to problems and perils of the administration — in other words, the balance between loyalty and discretion on the one hand and blowing the whistle on the other. And think through beforehand how you would handle being asked to do something illegal, immoral, unethical or just plain stupid.

Last, before going to work for a president who can be insulting, illogical, erratic, inappropriate and the like, it may be wise to find out the extent to which you would be expected to serve as a spokesperson or public defender of the administration’s positions, thinking and decisions. One has to be able to look oneself in the mirror every day and talk frankly to one’s family every evening. Once out of government, you want to be able to remember, and speak privately of your service with pride, firm in the belief that you emerged with your integrity, honor and reputation intact. All of the above, in fact, applies to experts in other fields as well — national security is just one of many areas of vital national interest in which the president will need significant help from people who didn’t want him to win.

Yes, Trump is a master of chaos with no core of belief. He would be a difficult boss. But as we mark another Veterans Day honoring those who have served our nation, you must not turn down a reasonable offer. At any point, you can go home, knowing that at least you tried. And that the country will be in your debt.