“U.S. Border Patrol Chief Michael J. Fisher is pleased to present the U.S. Border Patrol publication Holding the Line in the 21st Century, a trilogy of articles that outline the evolution of the Border Patrol’s border-security mission and strategy to achieve its goals. The first article, A Strategic Evolution: A Path to Border Security, explains the Border Patrol’s strategic shift in 2011 by providing a historical context from 2004 to the present and explains why the Border Patrol leadership made the shift. The second article, A Risk-Based Strategy: Targeting Illicit Networks, explains the implementation of the strategy, both in terms of the operational adjustments as well as programmatic developments to facilitate the strategic shift. Finally, the last article, Measuring Security: Risk Indicators Along the U.S. Border, attempts to answer the question “So how do we know we are winning?”