Republicans pilloried Hillary Clinton for what they claimed was her inadequate attention to security as secretary of state in the months before the deadly 2012 attacks in Benghazi, Libya. Congress even passed legislation mandating that the department’s top security official have unrestricted access to the secretary of state.

But in his first nine months in office, Mr. Tillerson turned down repeated and sometimes urgent requests from the department’s security staff to brief him, according to several former top officials in the Bureau of Diplomatic Security. Finally, Mr. Miller, the acting assistant secretary for diplomatic security, was forced to cite the law’s requirement that he be allowed to speak to Mr. Tillerson.

Mr. Miller got just five minutes with the secretary of state, the former officials said. Afterward, Mr. Miller, a career Foreign Service officer, was pushed out, joining a parade of dismissals and early retirements that has decimated the State Department’s senior ranks. Mr. Miller declined to comment.