Marco Rubio will be the first person, with the exception of Henry Kissinger, to hold the dual roles of secretary of state and national security adviser at the same time.
While many people have served in both positions in the course of their careers, including Colin Powell and Condoleezza Rice, they have always done so at different times.
On Thursday, President Donald Trump posted on his Truth Social platform that he is nominating Mike Waltz to be U.S. ambassador to the United Nations and that Rubio would be taking over as national security adviser in the interim.
Kissinger served as both secretary of state and national security adviser from September 1973-November 1975 under Presidents Richard Nixon and Gerald Ford, and no one has served in both capacities simultaneously since that time.
In 1969, Kissinger was appointed national security adviser by Nixon and he served as secretary of state from 1973-77, through the Ford administration.
He died in November 2023 at the age of 100.
Thus far into Trump's second administration, Waltz is the highest-ranking official to be reassigned to another position.
Prior to Trump's announcement that Waltz would be his next nominee to be ambassador to the United Nations, a White House source confirmed to Newsmax earlier Thursday that he was expected to leave his role as national security adviser "shortly."
Political correspondent Mark Halperin first reported that Waltz, deputy Alex Wong, and other members of the National Security Council were being ousted due to "general unhappiness" over how the panel is being run. According to Halperin, Waltz's leadership displeased the State Department, Treasury Department, and the White House.
The United Nations ambassadorship has remained open since Trump rescinded his nomination of Rep. Elise Stefanik, R-N.Y., over concerns about retaining the GOP's narrow majority in the House.
The new national security posting is one of several recent feathers in Rubio's cap.
In addition to his leading role at the State Department and his newly appointed role of interim national security adviser, Rubio is also currently acting administrator for the United States Agency for International Development (USAID) and the acting archivist at the National Archives and Records Administration.