Retired Lieutenant General Keith Kellogg served acting national security adviser to President Donald Trump following the resignation of Michael Flynn.

Kellogg, who served as an adviser to Trump during his campaign, was a candidate to remain in the position full time, but Trump eventually picked another military officer, Lieutenant General H.R. McMaster, as his new national security adviser on February 20.

Kellogg will return to his position as Chief of Staff and Executive Secretary of the National Security Council, a position he was appointed to by Trump in December 2016. He was at Trump’s Mar-a-Lago resort on February 20 when the McMaster pick was announced.

“Mr. President, thank you for the opportunity to continue to serve. I’m very honored by it, very privileged by it,” Kellogg said. “And I’m very honored and privileged to serve alongside with H.R. McMaster, I’ve known for years as well. He’s a great statesman, a great Sargent. Thank you, sir.”

Trump told reporters, “”What a team. This is a great team. We’re very, very honored. Our country is lucky to have two people like this and frankly, after having met so many of the people in the military, we’re lucky to have all of them.”

Flynn resigned on February 13 amid reports that he had spoken with Ambassador Sergey Kislyak about Russia sanctions, despite Flynn repeatedly claiming that he never did so.

Here’s what you need to know about Keith Kellogg.

1. He Is a Retired U.S. Army General Officer

Executive Secretary of the National Security Council Lieutenant General Joseph Keith Kellogg Jr. #5Days #TeamTrump ?????????? pic.twitter.com/PVSQv5ular — Deplorable Patriot (@Deplorable_1776) January 15, 2017

Like Michael Flynn, Keith Kellogg served in the U.S. Army prior to being appointed to Donald Trump’s National Security Council.

Kellogg served in the 101st Airborne Division during the Vietnam War, and he commanded the 82nd Airborne Division starting in 1996.