Retired Navy Adm. Mike Mullen candidly shared his experiences as a military leader with the National Geospatial-Intelligence Agency workforce Oct. 14, in Springfield, Virginia, as part of the agency’s distinguished speaker series.

NGA Director Robert Cardillo opened the event by recalling his 2009 “summer vacation” working for Mullen on the joint staff.

“It was a Ph.D. education in our profession,” said Cardillo. “To be able to not only work for the admiral, but for all the joint staff and to see and feel — most importantly to feel — the visceral impact of our provision of service, again, was an enormous gift.”

Cardillo’s experience working for Mullen left a profound impression on him and directly led to the NGA intent and the director’s emphasis on consequence, he said.

“I was always impressed with the way the admiral was able to cut through very complicated issues, of enormous economic, and social, and cultural, and religious — and yes, militarily-vexing challenges — and find that leadership point of inflection,” said Cardillo.

Mullen spent more than 43 years in the military, including his final post as chairman of the Joint Chiefs of Staff, the highest-ranking official in the armed services. Among his achievements in that role was the 2010 elimination of the “don’t ask, don’t tell” law that barred gays from openly serving in the U.S. military.

Throughout his remarks, the former chairman encouraged junior staff and subordinates to speak up and challenge status quo.

“If you are sitting on something that no one is listening to — how are you going to get that on the table, in front of leadership — when no one between you and the leader wants that to happen? How you do that, as part of who you are … is a real challenge.”

One of the lessons that guided him as a leader came in a letter he received when he was promoted to admiral, he said.

“Just remember from now on, you will always eat well, and you’ll never hear the truth again,” said Mullen.

To combat that, the admiral said he encouraged those with diverse viewpoints, especially junior staff, to challenge him as a leader.

“It’s about talent,” he said. “Making sure you have the best talent in the room and creating opportunities for that talent.”

These efforts help prepare leaders for the future, said Mullen. So does taking on hard jobs and constantly seeking challenges.

“If you’ve become comfortable in your leadership position, it’s time to move aside” said the admiral. “You’ve got to continue to grow.”

Encouraging engagement, transparency and collaboration are also clear components for successful leadership, he said.

“I believe in people,” said Mullen. “Delegating trust, relationships and empowering those who work for me to be bigger than who we are in a world that demands it.”

Since retiring from the Navy, Mullen has joined the boards of General Motors, Sprint and the Bloomberg Family Foundation. He is also a visiting professor at Princeton University’s Woodrow Wilson School of Public and International Affairs.