President Barack Obama nominated longtime Defense Department understudy Ashton Carter as his fourth defense secretary on Friday to replace Chuck Hagel, the lone Republican in Obama’s Cabinet, who resigned last week after disagreements with the White House.

In Carter, Obama gets a policy expert who has worked for 11 defense secretaries. The 60-year-old Carter pronounced himself ready to give Obama candid, strategic advice once he clears U.S. Senate confirmation, which should move fairly quickly.

Carter will take charge as the U.S. military fights Islamic State militants in Iraq and Syria, helps combat Ebola in West Africa, winds down in Afghanistan, and continues to deal with spending cuts from Congress, Obama said.

“He knows the Department of Defense inside and out, all of which means that on Day One, he’s going to hit the ground running,” Obama said.

Obama praised Carter for his “true regard, his love for men and women in uniform and their families” and credited Carter with rushing body armor and vehicles to troops in Iraq and Afghanistan dealing with roadside bombs.

Hagel had privately expressed frustration with the administration’s strategy on Iraq and Syria and at his lack of influence over decisions. Officials have said Hagel did not always speak up at meetings and seemed out of his depth on the Middle East.

Hagel had been scheduled to attend the small ceremony in the Roosevelt Room of the White House, but at the last minute a defense official said Hagel would not be there because he “does not want in any way to detract from or distract” from Carter’s nomination.

In brief remarks, Carter told Obama that if he is confirmed, “I pledge to you my most candid strategic advice.”