Since President Felipe Calderon took office in December 2006, Mexico has embarked upon the implementation of a culture of law and security that has triggered a war with organized crime. This war has involved all sectors of society and has activated a series of renovations in its armed forces, which to date remain the most trusted institutions in Mexican society. This groundbreaking Letort Paper is an important contribution to an understanding of the structure, culture, motivators, and challenges of the Mexican military in the 21st century. Mr. Inigo Guevara Moyano, a Mexican researcher and writer, provides a clear picture of doctrinal and structural transformations, adaptations, and improvement that the Mexican armed forces have endured over the past 5 years. Mr. Moyano focuses on how the counternarcotic role has impacted its organization, deployments, and operations, and how it has generated new doctrinal and equipment requirements. The paper also addresses key areas of national and international concern such as respect for human rights and and the military justice system. Given Mexico's importance to the United States as its neighbor, ally, and third largest trading partner, understanding the transformation that its armed forces are enduring to assist in the implementation of a culture of law should be of prime concern to all actors-government, private sector, and academia-involved in the decisionmaking process."