Mexico has become a paradise for the nota rosa, or red press, those sections of our media that focus on sensational crime and violence. Since 2006 the violence has reached unheard-of levels and crosses all social boundaries. Drug traffickers, the police, military chiefs, politics and business have become intertwined in a spectacular way.

The latest bloody event is the appearance of 49 bodies without hands, feet or heads on the road near Cadereyta, a town very close to Monterrey, the capital city of the prosperous northern state of Nuevo León. Beside the bodies there was a banner apparently claiming responsibility for the murders on behalf of the notorious Los Zetas cartel. The number of executions in Nuevo León so far this year is 666, more than the 611 murders committed by organised crime in the past year.

It is the third such massacre in the country in the last 10 days, and the fifth in 10 months. Earlier in May 23 bodies were found – some lying and others hanging from a bridge - in the neighbouring state of Tamaulipas. Last week, 18 bodies were thrown on to a road in Jalisco. In September 2011, 18 corpses appeared in the state of Veracruz, and in November 26 murder victims were found in two abandoned trucks in Guadalajara.

Los Zetas is a group of drug traffickers who until 2010 worked for the powerful Gulf cartel. It was formed by military men from the Grupo Aeromóvil de Fuerzas Especiales (GAFE), an elite corps of the Mexican army, trained by the CIA. It is in conflict with the Sinaloa Cartel, headed by Joaquin "El Chapo" Guzmán and El Mayo Zambada over drug-trafficking routes and markets in Mexico and smuggling to the US. Several analysts consider it the most violent criminal gang in Mexico.

The massacre of 49 people in Cadereyta is part of the struggle between cartels for the strategic city of Monterrey, the economic powerhouse of northern Mexico and home to a dynasty of powerful and usually conservative businessmen. The city gives shelter to the drug barons and provides them with logistical support and income from extortion. They have become prominent members of the community.

The drug cartels conquered Monterrey and turned it into their sanctuary. Many of the bosses live in the richest residential areas of the city. Their sons attend the best private universities and move among the local elites. Casinos, spas and brothels flourish under their auspices.

But after 2006 violence erupted in the state. In 2009 the local station, Televisa was attacked with rifles. In August 2011 more than 50 people, most of them women, died when a casino was set on fire. Violent blockades of main avenues by armed groups are also frequent. The cartels have even mobilised the city's poor in their favour.

Diplomatic cables coming out of the US Consulate in Monterrey, written between 2006 and 2007 and revealed by WikiLeaks, alerted the world to the fact that the city had become a narco war zone. At the end of 2009 Bruce Williamson, then US consul in the city, said in a report to the Department of State that Nuevo León was "Zeta territory" and that the fight against drug traffickers was producing no results in that part of the country. Three years on, that estimation has proved tragically right.

The slaughter in Cadereyta is the latest tragic testimony of the failure of the war on organised crime launched by President Felipe Calderón. The nation is now more insecure than when he assumed office in 2006.

The story of the Calderón administration is being told in the crime pages of the papers, not in the articles and speeches of its officials. His term will pass into history as one that saw human rights violations, public insecurity, the military on the streets, more than 60,000 dead and 10,000 disappeared.

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