The sickening discovery this week of 11 headless bodies heaped like broken dolls near the colonial city of Merida underscored a bitter lesson for Mexico: The battle to control the multibillion-dollar drug trade knows no boundaries.
The bodies are piling up nationwide, even in normally tranquil and touristy spots such as Merida, not far from the Maya ruins of Chichen Itza.
During a seven-day period ended Friday, more than 130 people died violently throughout the country. Headless bodies turned up in four states, including Baja California.
The Yucatan peninsula, strategically close to smuggling routes through Central America, tallied 12, after another decapitated body was found a few hours later Thursday about 80 miles east of the carnage near Merida.
Mexico's drug wars used to play out mainly in smuggling battlegrounds along the U.S. border, such as Tijuana and Ciudad Juarez. But a crackdown launched 21 months ago by President Felipe Calderon has exacerbated feuding among drug traffickers for control of smuggling routes.
As a result, the country convulses with daily violence that shows a new and disturbing geographic reach and viciousness.
"The bottom line is you've got a major internecine battle, a kind of civil war among drug cartels," said Bruce Bagley, a security and drug-trafficking expert at the University of Miami. "It has intensified because the stakes are high. There's a great deal of money to be made."
But traffickers are keenly aware of the psychological effect on enemies and ordinary Mexicans when they chop off rivals' heads and leave threatening notes with the remains.
Some analysts say tactics such as beheadings, once unheard of in Mexico's drug underworld, are akin to terrorism because part of the goal is to scare civilians so that they will press the government to back off. Calderon has sent 40,000 troops and 5,000 federal police officers into the streets as part of the campaign against organized crime.
"You're sending a signal to the Calderon government, to the police, that you mean business," said Fred Burton, vice president for counter-terrorism at Stratfor, an Austin, Texas-based intelligence firm. " 'This is the result when you don't play ball with us.' "
Last week, the Calderon government announced a broad new blueprint for fighting crime, including better coordination between federal and local authorities, new federal prisons, improved tracking of cellphones and tougher steps against money laundering.
Calderon administration officials said Thursday night that the Yucatan beheadings and other spectacular displays of violence show that arrests and drug seizures have hurt the cartels, prompting them to lash out with increasing savagery.
"They have to respond in a symbolic way that creates uncertainty in the public -- this is what they have been doing during the last months," Atty. Gen. Eduardo Medina Mora said late Thursday during an interview on Mexican television.
Since Saturday, Mexico has tallied at least 136 killings across 18 of its 31 states, according to Mexican news media accounts. They included especially brazen attacks:
* On Thursday, the day the headless bodies were found near Merida, gunmen stormed a house in the Pacific state of Guerrero, killing two women and two girls, ages 8 and 12. Two police officers were ambushed and slain in a gun battle as they raced to the home.
* An armed group battled Mexican troops Wednesday in the central state of Guanajuato. Four gunmen died and two soldiers were wounded.
* Four decapitated bodies turned up Tuesday in Tijuana. Those killings appeared to be linked to a power struggle between drug traffickers who once collaborated as part of the Arellano Felix gang. Headless bodies also were found in Sinaloa and the northern state of Durango.
Two weeks ago, a hit squad killed 13 people, including a 16-month-old boy, at a family gathering in the northern town of Creel, a tourist gateway to the scenic Copper Canyon region.
Hardly a day goes by without new accounts of violence. Unofficial tallies by Mexican news outlets put the death toll from drug violence this year at more than 2,600. By some counts, it has already exceeded the total for 2007, which set a record.
Police officers have died at an alarming rate. The daily Milenio newspaper reported Friday that 71 officers had been slain nationwide in August -- the highest monthly toll since Calderon launched his crime offensive in December 2006.
Some of Mexico's more than 300,000 local and state police officers have been killed by drug hit men while carrying out their duties. But others have worked as hired gunmen for drug smugglers, and become targets of rival gangs. when one gang takes on another.
The violence has left Mexicans increasingly unsettled. They are unnerved by the steady stream of bloody news and pessimistic about the government's odds of winning, polls show. Many Mexicans tend to view the drug killings as largely a matter among criminal gangs, but the violence is increasingly claiming innocents, and showing up in new spots.
The Yucatan peninsula, though part of an important coastal smuggling corridor for cocaine shipped from Colombia, has not traditionally been a place where drug traffickers have battled.
But it has become an increasingly important transit route for narcotics relayed by land from neighboring Guatemala. That, and a growing local market for illegal drugs, has heightened competition for control, Bagley said.
Traffickers have resorted to decapitating rivals during the last two years.
Thursday, a young farmer came upon the heap of bodies, which according to some Mexican news accounts were covered with tattoos and bore signs of torture. Some of the accounts speculated that the killings might have been the work of the Zetas, a group of paramilitary-style hit men for the Gulf cartel who are known for extreme violence.
Gov. Ivonne Ortega Pacheco said in a television interview that anonymous callers had been demanding that authorities remove road checkpoints "and let them work." Ortega said the callers became more menacing about two weeks ago, threatening that bodies would start to turn up.
But Ortega said the roadblocks would remain in place. In a separate broadcast message, she sought to reassure Yucatan's residents.
"Yucatan is a peaceful state of hardworking people," she said. "We can't let any lawbreakers affect our families' tranquillity."
As Ortega spoke, news reports were circulating of the discovery of four bodies, 1,500 miles away in the northern border state of Sonora. Three had been beheaded.