The demise of Colombia’s Medellín and Cali cartels in the early 1990s created space for Mexican cartels, previously more involved in the transit of cocaine between North and South America. Alliances formed between previously disparate groups of Mexican traffickers and small family drug businesses based in the ‘Golden Triangle’ of Sinaloa, Durango and Chihuahua. Competition for control became intensely violent and often involved coercion and corruption; many contracted ruthless bands of mercenary hitmen. Despite moderate attempts by former president Vicente Fox to clamp down on the violence through initiatives such as Operation Secure Mexico and the Northern Border Initiative in 2005 and 2006 respectively, levels of violence rose. In 2006, Felipe Calderón assumed the presidency and immediately declared ‘war’ on the cartels, deploying more than 40,000 soldiers to states across the country. Calderón pushed for enhanced cooperation between Mexico and the United States on security issues. Despite investing funds and political capital in fighting the cartels, Calderón received much criticism for the rapid rise in drug-related killings, resulting in approximately 60,000 murders between 2006 and late 2012. His successor, Enrique Peña Nieto, implemented a paramilitary police force inspired by the French Gendarmerie. However, after a gradual decline in criminal violence in 2012–2014, murders began to increase again in 2015. Police and local political figures were accused of involvement in a number of crimes, raising questions about the country’s institutional strength. Calderón’s militarised strategy broke up some of the biggest cartels, resulting in a less stable and therefore more violent criminal underworld. Some groups that worked as enforcers of big cartels saw the opportunity to initiate their own empires. One of these violent criminal enforcers, Los Zetas, broke from the Gulf Cartel and introduced a new wave of brutal and highly visible assassinations – often conducting massacres or dumping decapitated or mutilated bodies in public spaces. Los Zetas later became one of the most powerful criminal groups in Mexico, before declining around 2014. Other groups imitated its violent tactics – the most successful of which was the Jalisco New Generation cartel, which became a major criminal player in 2015. There is a real concern that organised crime and the armed violence linked to it is affecting Mexico’s international reputation and economic performance, despite a series of reforms introduced by Nieto.