There has been much to criticize about President Donald Trump’s handling of America’s national security, including his recent declaration of a national emergency on the southern border. But while that declaration might be misguided, Trump has been right about one thing: The United States has never developed an effective strategy for the actual security challenges south of the border. Since the United States became a global power in the 20th century, it has used a sequenced method for addressing emerging threats—first building an understanding of them, then developing a working consensus among security experts and political leaders, and then relying […]