Michael Anton, the director of Policy Planning Staff at the State Department, will leave the department this fall, the Trump administration has confirmed. He served in key roles in the administration’s foreign policy initiatives, including as the technical lead for the Iran nuclear negotiations and the lead author of its national security strategy.

Anton worked for the National Security Council during the George W. Bush administration and served as deputy assistant to the president for strategic communications during the first Trump administration. His 2016 essay “The Flight 93 Election,” which argued that electing Donald Trump was necessary for the survival of American civilization, launched him into the position of one of the MAGA movement’s key intellectuals.

The reason for Anton’s exit, and whether he will remain in the administration in some other capacity or remain entirely, have yet to be confirmed.