The Defense Department’s top policy director submitted a letter of resignation Feb. 19 saying he will leave his post at the end of the month, stating plainly that his departure was prompted by President Trump.

Undersecretary of Defense for Policy John Rood assumed his role in August 2018, and will be succeeded by James Anderson, Assistant Secretary of Defense for Public Affairs Jonathan Hoffman told reporters on Wednesday. Anderson, who was Senate-confirmed in August 2018 as the assistant secretary of defense for strategy, plans and capabilities, has been performing the duties of Rood’s deputy since the position was vacated last July with the retirement of Deputy Undersecretary for Policy David Trachtenberg.

Rood’s resignation letter, obtained by Defense Daily, makes clear that he feels his departure was forced by senior administration leaders, including the president.

“Mr. President, It’s my understanding from Secretary [Mark] Esper that you requested my resignation … therefore, as you have requested, I am providing my resignation effective February 28, 2020,” the letter said. Rood’s resignation and imminent departure were first reported by CNN. Trump soon confirmed the news in a tweet, saying, “I would like to thank John Rood for his service to our Country, and wish him well in his future endeavors!”

As the Pentagon’s chief policy leader, Rood played a key role in developing and overseeing the department’s various policies and plans. Hoffman noted in particular his role in implementing the department’s 2018 National Defense Strategy, and overseeing the development of the latest Missile Defense Review, a strategy to outline and execute the nascent U.S. Space Force, as well as emphasizing nuclear deterrence capability needs via the Nuclear Posture Review.

Rood said in his letter that he was proud of the policy team’s leadership and accomplishments on efforts including honing the department’s focus on threats from China, developing new cyber authorities and policies, rebuilding alliances in the Middle East and gaining more burden-sharing agreements from allies and partner nations.

“I leave with the utmost admiration for the outstanding team with which I worked at the Defense Department,” he said. Before taking his current post, Rood spent over 20 years in the U.S. government within the Departments of State and Defense, the National Security Council and Central Intelligence Agency and as a staff member in the Senate. He also previously served for a decade in the private sector, including as senior vice president of Lockheed Martin International [LMT], and as a vice president at Raytheon [RTN].

Upon the news Wednesday, sources and analysts questioned whether Rood’s role in the situation involving the Pentagon withholding of U.S. military aid to Ukraine that led to Trump’s impeachment by the House of Representatives was the reason behind his forced resignation. Rood had reportedly certified that Ukraine was meeting the terms of its agreement to receive $250 million in weapons and aid.

Hoffman said considering a potential tie-in between Rood’s role in the Ukraine issue and his resignation submission would be “speculative” and that Rood’s letter “speaks for itself.”

“I have no information that would lead me to that conclusion,” Hoffman said.

“The president has the opportunity and the ability to have the team that he wants to have in policy positions in federal government; that’s why we have political appointees,” Hoffman continued. “The president can make a decision to go in a different direction, so I’m not going to speculate on the motivations.”