In March 2025, volunteers searching for missing relatives in Mexico entered an abandoned ranch that had served as a drug cartel recruitment and training center in the state of Jalisco. As the press would recount, they found charred human remains alongside bone fragments, bullet casings, and hundreds of shoes and other articles of discarded clothing. The discovery shocked a country where, according to official government statistics, close to 130,000 people have “disappeared” since 1962. Brutal violence unleashed by drug cartels and other crime groups has left a staggering death toll—estimated by the United Nations to be around 30,000 murders per year since 2018.

Further south, in the first four months of 2025, Colombia saw the worst outbreak of violence since the 2016 signing of a peace agreement between the government and the country’s largest guerrilla group, the Revolutionary Armed Forces of Colombia (FARC). Battles between FARC dissidents and guerrillas of the National Liberation Army (ELN) in an area rife with coca cultivation and cocaine trafficking forced the displacement of close to 65,000 civilians and caused the deaths of 117. Since the peace accord, armed groups in Colombia have proliferated, bringing staggering levels of violence to rural areas and towns in their efforts to control lucrative illicit economies.

These developments provide an important backdrop for evaluating Paul Angelo’s outstanding and prodigiously researched study of US-backed security sector reform in Colombia and Mexico. Angelo draws on an impressive array of Colombian, Mexican, and US scholarly sources on criminal and political violence and governmental efforts to contain it. His research is complemented by personal interviews and communications, as well as the experience gleaned during Angelo’s three deployments to Colombia, where he planned inter-agency missions in support of US assistance policy as a US naval officer.

Angelo compares Plan Colombia (2000–2011) and Plan Mérida (2007–2016), “two of the most high-profile instances of US-backed security sector reform globally” (p. 8). In Colombia and Mexico, state authority and legitimacy were under attack by violent actors—the at times overlapping nexus of drug traffickers, paramilitaries, and insurgent groups in Colombia, and drug cartels in Mexico. The US government spent billions of dollars to provide host countries with the equipment, training, and intelligence to rein in the violence and enhance democratic governance, human rights, and the rule of law, even if, in practice, all goals were not accorded the same priority.

Angelo identifies similarities between the two countries that allow for useful comparison: the “staggeringly high levels” (p. 32) of insecurity, the incapacity of state forces to confront the challenges posed by non-state actors, and the similar design and goals of US assistance packages. He also acknowledges important differences. In Colombia, the state was absent from large parts of the national territory in terms of security and social services, whereas the Mexican state was present, albeit weak and corrupt. Moreover, while both Mexico and Colombia faced violent cartels focused on profiting from various illicit economies, Colombia also battled insurgent and paramilitary organizations with political and ideological goals. Finally, while Colombia was eager for US assistance, the history of US interventionism in Mexico created heightened sensitivity to issues of sovereignty, complicating US involvement.

Angelo argues that reforms succeeded in Colombia in reducing the violence, increasing the effectiveness of the armed forces and police, and enhancing civilian support for security institutions, even if the situation eventually unraveled. By contrast, Mexico’s security sector had little success in containing the violence and became increasingly involved in corruption and human rights violations. Angelo argues that domestic factors are key to understanding the different outcomes. He grounds his comparison in three variables: the presence of private sector support for security institutions and reform; the degree of political consensus or polarization over security policy across administrations; and the degree of centralization of the security sector itself.

With respect to private sector support, Angelo references political scientist Gustavo Flores-Macías, who has demonstrated that security crises open opportunities to increase elite taxation. In Colombia, the concern of business elites over personal safety grew in proportion to the FARC’s practice of kidnapping for ransom as they targeted urban areas in the late 1990s. The sense of vulnerability, combined with the collapse of peace negotiations with the FARC under President Andrés Pastrana, led the business sector to support a security tax on wealthy individuals proposed by President Álvaro Uribe in 2002. In Mexico, however, cartel violence had less of an impact on private sector elites, leading to a lack of support for President Felipe Calderón’s frontal assault on cartels at the outset of his presidency in 2006. Angelo notes the important exceptions of Ciudad Juárez and Monterrey in northern Mexico, where spiraling rates of homicide and extortion posed an existential threat to the business community, leading to successful public–private collaboration to improve security.

Degrees of political polarization also differentiate the two cases. Referencing Scott Mainwaring and Timothy Scully’s work on party system institutionalization, Angelo shows how the severity of the security threat in Colombia initially “inspired convergence and reduced polarization” among parties (p. 200) during the years of Plan Colombia, even in a political system characterized by low party unity. By contrast, security policy in Mexico was highly politicized and partisan, with congressional opponents and successive administrations attacking both their predecessors’ policies and the idea of cooperation with the United States.

Angelo’s third axis of comparison concerns the role of security force centralization or decentralization. He argues that Plan Mérida was undermined by the multiplicity of security institutions and the absence of a central authority. Decentralization not only worsened insecurity but also converted local security officials into “agents of local political and often criminal power” (p. 258). In Colombia, by contrast, centralization and unified chains of command facilitated reforms, inter-branch coordination, and cooperation with the United States.

Angelo grimly documents the failure of Plan Mérida: a tripling of the homicide rate between 2007 and 2017, a six-fold increase in opium poppy cultivation, an increase in the transshipment of cocaine and fentanyl, and a worsening human rights crisis. Changes in administrations in Mexico and the United States produced policy swings that did little to reverse these trends and, in many ways, accelerated them. Mexico today is beset by cartel violence, human rights abuses by local police forces, as well as the infiltration of the police by organized crime.

Plan Colombia produced impressive security gains through 2011, including improvements in indicators of violence, reductions in coca cultivation, and military advances against the FARC that paved the way for peace negotiations in 2012. Angelo posits that the sustainability of these gains was undermined by the intense political polarization over the peace process that spilled over into the security forces themselves.

Overall, Angelo overstates Colombia’s successes of 2000–2011, which appear more tactical than strategic. Despite efforts to couple greater security with the state’s provision of social services in conflictive areas, the government never spread effective state authority throughout Colombia’s territory. Similarly, the failure of state forces to occupy the spaces vacated by the FARC following their 2016 demobilization created a vacuum now exploited by numerous FARC splinter groups, the ELN, and drug trafficking organizations.

Angelo acknowledges the severity of Colombia’s “false positives” human rights scandal, in which the armed forces killed innocent civilians and dressed them in guerrilla uniforms to inflate body counts. But he underplays the Uribe administration’s failure to curb paramilitary violence during the early years of the democratic security policy, as well as the United States’ own double standard toward guerrilla and paramilitary abuses. In addition, the book would have benefited from a more nuanced treatment of the tensions between the counter-narcotics and counterinsurgency missions at the outset of Plan Colombia. Finally, by emphasizing domestic variables in Colombia and Mexico, Angelo sidesteps the ways drug-consuming countries fuel violence in Latin America, both through the constant demand for drugs and the supply of high-powered weapons that make cartel violence all the more lethal.