I first met then-Lt. Col. John Kelly when he was the Marine Corps liaison to the House of Representatives, and I was speaker of the House. We traveled together on a number of overseas trips. He was the best liaison officer I have worked with in any service.

Even then, Kelly was smart, diplomatic, personable, a good listener – and knew how to get things done. I found him short on words and long on wisdom.

Gen. Kelly later served multiple tours in Iraq, where he excelled. He understood the military challenges there, but even more importantly he understood the cultural and political challenges.

His last active duty assignment was serving as commander of the Southern Command. I visited him at SOUTHCOM headquarters and was deeply impressed with his grasp of Latin American economics and politics, as well as the challenges posed by organized crime.

I was delighted when Gen. Kelly agreed to serve as secretary of Homeland Security. I thought he brought with him a unique understanding of the challenges we face at our border and with violent multinational gangs. In fact, I thought the choice of Kelly was a good indicator of the caliber of people then-President-elect Trump wanted in his Cabinet.

On several occasions, I have had the opportunity to discuss a wide range of homeland security issues with Secretary Kelly. Every time, he impressed me with how much he understood, how clear his plans were, and how effective his implementation was going to be.

President Trump has made a big decision in bringing Kelly to the White House to be chief of staff.

It will be fascinating to watch these two powerful, experienced leaders forge a unique working relationship.

I predict the White House will become more orderly and disciplined – with clear lines of authority, serious planning and strong teamwork.

The person who may benefit most from this change is President Trump. He has worked with many smart, successful people in his remarkable career, but he has never worked this closely with someone as used to command, organization and dignified insistence on teamwork as Secretary Kelly.

If these two powerful leaders truly become a team, the Trump presidency will become one of the most effective in our history.