The United States-Mexico border is in its most secure condition in living memory. Illegal border crossings are at historic lows unseen for decades. But an increasingly powerful Mexican drug cartel poses a growing challenge to U.S. national security and Mexico’s sovereignty. The group in question, the Jalisco New Generation Cartel, or CJNG, is gradually destabilizing several Mexican states and displacing other cartels that previously exerted prime influence over Mexican politics.