It turned out to be easy to undermine West Point. All it took was an executive order from President Trump and a memo from Defense Secretary Pete Hegseth dictating what could and couldn’t be taught in the military and its educational institutions.

In a matter of days, the United States Military Academy at West Point abandoned its core principles. Once a school that strove to give cadets the broad-based, critical-minded, nonpartisan education they need for careers as Army officers, it was suddenly eliminating courses, modifying syllabuses and censoring arguments to comport with the ideological tastes of the Trump administration.

I will be resigning after this semester from my tenured position at West Point after 13 years on the faculty. I cannot tolerate these changes, which prevent me from doing my job responsibly. I am ashamed to be associated with the academy in its current form.

The trouble began around the time Mr. Trump was sworn in for his second term as president. That week, West Point administrators pressured me to withdraw an article about the military’s obligation to be politically neutral that had been accepted for publication at the national security blog Lawfare. The administrators did not find fault with the article but said they were worried that it might be provocative to the incoming administration. Reluctantly, I complied.

Then came the executive order from Mr. Trump on Jan. 27 and Mr. Hegseth’s memo two days later. Mr. Trump’s order prohibited any educational institution operated by the armed forces from “promoting, advancing or otherwise inculcating” certain “un-American” theories, including “gender ideology” and the idea that “America’s founding documents are racist or sexist.”

Mr. Hegseth’s memo went further, adding that the service academies were prohibited even from providing instruction about such topics. Mr. Trump and Mr. Hegseth also ordered that the academies shall “teach that America and its founding documents remain the most powerful force for good in human history.”