In this monograph, Dr. Mark Moyar, Brigadier General (retired) Hector Pagan, and Lieutenant Colonel (retired) Wil R. Griego analyze United States Special Operations Forces' (USSOF) assistance to Colombia in the context of decades of counterinsurgency and counternarcotics operations. While the case of Colombia is often cited as an exemplar of global Special Operations Forces (SOF) foreign engagement, the details of the engagement, and the reasons for its success, have not previously been addressed in a scholarly publication. This study represents the first comprehensive analysis of the persistent SOF engagement in Colombia. It draws upon the collective wisdom of numerous U.S. and Colombian government personnel, and the authors' own decades of experience in Colombia and other countries where the United States has undertaken prolonged partnership.The authors attribute the success of SOF engagement in Colombia to the long-term development of human capital in the Colombian security forces. As trainers, educators, and advisors, U.S. special operators helped nurture Colombian officers and NCOs who would rise through the ranks into key positions of leadership. The huge improvements in Colombian counterinsurgency and counternarcotics performance were the result, first and foremost, of dedicated and skilled Colombian leaders