When I reopened the U.S. Embassy in Afghanistan after the fall of the Taliban, Mr. Hagel was an early visitor to Kabul who understood the long-term strategic importance of America’s engagement in Afghanistan and relationship with Afghan President Hamid Karzai. He has remained consistent, under Presidents Bush and Obama, in his support for that engagement—for maintaining a presence of troops and other assets to ensure that no strategic threat to the U.S. could ever again emerge from Afghanistan.

I hosted Mr. Hagel in 2006 while serving as U.S. ambassador to Pakistan, and once again he impressed me with his grasp of the complexity and significance of the challenges America faces there. He understood that Pakistan, while far from a perfect ally, was an indispensable partner.

I still remember his frank but nuanced conversation with Pakistan’s then-president, Pervez Musharraf, and the message he carried back to Washington: The U.S. has to implement a multidimensional policy of pressure and support, adjusted to fit prevailing circumstances. Above all, America needs to demonstrate strategic patience—a sense that it is in this relationship for the long run and won’t abandon the region as in the early 1990s, a decision that inadvertently paved the road to 9/11. It was the right policy then under one president and it is the right policy now under another.

These experiences taught me that Chuck Hagel is a statesman, and America has few of them. He knows the leaders of the world and their issues.