Private militias have provided criminal groups with greater mobility and fighting power, enabling them to engage in large-scale violence and seek control of criminal markets and territories beyond their home towns. The Mexican case highlights the need for democratic elites to reform authoritarian judicial and security institutions and to punish state agents who protected organized crime, in order to prevent the intertwining of democratic politics and the criminal underworld.

The spread of subnational party alternation in states with drug trafficking routes and the proliferation of private militias led to the outbreak of intercartel wars. The development of private militias allowed cartels to contest their rivals' control over drug trafficking territories, leading to largescale criminal violence.

political alternation and the rotation of parties in state gubernatorial power undermined the informal networks of protection that had facilitated the cartels' operations under one-party rule. Without protection, cartels created their own private militias to defend themselves from rival groups and incoming opposition authorities.

The power dynamics shifted when the Colombians began paying Mexican traffickers in product rather than cash, allowing the Mexicans to invest in their own drugs. This led to Mexican gangs controlling 90% of the cocaine entering the United States, worth an estimated $70 billion a year.

The Zetas' business model was based on imposing protection fees on businesses, including illegal activities such as drug trafficking, and licit businesses such as farming and shopkeeping. Those who refused to pay were killed or threatened with violence. This led to a culture of fear and intimidation, where businesses were forced to pay protection fees to avoid violence. The violence in Mexico was further fueled by the struggle between powerful groups for control of drug protection rackets and the pursuit of aggressive counternarcotics policing. This led to a cycle of violence, where struggles between rival groups sparked aggressive policing, and aggressive policing generated increasing struggles between rival groups.

The sale of drugs was no longer limited to tourist areas and border cities, but spread to small towns and rural areas. This led to an increase in violence as local drug gangs fought over control of drug-selling areas.

In Mexico, drug traffickers began selling drugs in bulk to the domestic market, leading to an increase in drug use and addiction.

The violence in Mexico escalated due to several factors, including changes in American narcotics demands, the gun market, and criminal practices in Mexico. The availability of guns increased after the ban on semiautomatic assault weapons was lifted in 2004, leading to a global boom in gun manufacture and sales.

New organizations emerged, armed with high-caliber weapons and prepacked political creeds and religious messages. The Familia Michoacana, a Sinaloa-linked group, tossed the heads of five Zetas into a Michoacán bar, declaring that they did not kill for money, but for divine justice. The conflict continued to spread throughout Mexico, with cartels fighting each other, and soldiers and police often caught in the middle.

extort small-time smugglers, torturing and killing those who refused to pay.

In the mid-1990s, the Gulf Cartel recruited members of the Mexican army special forces, known as the Zetas, leading to an increase in violence connected to the drug trade.