John Kelly, the retired Marine four-star general who is Donald Trump’s reported pick to head the Department of Homeland Security, is admirably suited to defending U.S. borders. More surprisingly, he may also moderate some of Trump’s more extreme positions on illegal immigration — which would help both the U.S. and its neighbors.

During his three-year-plus stint as head of the U.S. Southern Command, Kelly focused on the threat posed by Latin American drug traffickers who supply almost all of the cocaine, heroin and methamphetamine entering the U.S. He also warned repeatedly that the same smuggling networks that facilitate the trade in drugs, illegal workers, sex slaves and endangered wildlife could also enable the infiltration of terrorists.

Yet Kelly’s approach wisely went beyond interdiction and military training and support. As he told Congress, “95 percent of my efforts are not military. It’s economic development.”

Kelly was a champion of the Alliance for Prosperity, the nearly $1 billion program of assistance for Central America passed last December by Congress with bipartisan support. It concentrates not just on law and order, but also on strengthening institutions, building infrastructure and promoting regional integration.

In dealing with the U.S.’s southern neighbors, Kelly has stressed the idea of partnership. He knows how important it is to share intelligence, for instance, and how that in turn requires cooperation rather than coercion. And he’s acknowledged that the flow of people from Central America to the U.S. is driven partly by gang violence associated with the U.S. demand for illegal narcotics.

He knows, as he himself put it, that “a wall by itself will not work.”

Persuading his boss and Cabinet colleagues to adopt a more enlightened — that is, comprehensive — approach to border control and illegal immigration will be one of his biggest challenges. Effective border control, after all, must also enable the speedy passage of legitimate commerce. As border patrol and immigration enforcement bulk up, better training and anticorruption screening will be essential. And the Department of Homeland Security has a role in continuing support for the Alliance for Prosperity’s programs.

Kelly’s new department — the third-largest in the federal government — isn’t just about the border. It encompasses everything from customs agents and airport security personnel to the U.S. Coast Guard, the Federal Emergency Management Agency and the Secret Service. More than a decade after its creation, the department remains a Frankenstein of ill-assorted parts, not always working together as intended. Adding another general to the incoming administration is well and good, so long as he also proves to be a excellent manager. Securing the border will be hard; so, too, will be running the Department of Homeland Security.

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