On Friday, the Obama administration bid farewell to General Keith Alexander, the longest-serving head of the National Security Agency. Defense Secretary Chuck Hagel paid tribute to Alexander’s tenure.

Defense Secretary Chuck Hagel: “Our responsibility, all of us, whatever the revolutions in technology, is to guard not only our nation, but also the fundamental character of our open society. General Alexander, your vision, your dedication, your leadership have allowed us to begin that task. Now it is ours to carry. From a grateful nation, thank you, Keith.”

Alexander will be replaced by Admiral Michael Rogers.