To strike back at narcotics traffickers suspected of ordering the assassination of Mexico's top drug cop, President Felipe Calderon dispatched 2,000 army troops and federal police to the gang's home base, the western state of Sinaloa.
The traffickers struck back themselves with a paramilitary-style ambush of a police station, and taunted the newly arrived troops with mocking signs on the streets.
Analysts say those moves last week show that the killing of Edgar Millan Gomez on May 8 has opened a dangerous new phase in the country's drug war.
Millan Gomez, the 41-year-old acting director of Mexico's federal police, knew he was a target, and he shuttled among three homes in a bid to outwit his nemesis: Arturo Beltran Leyva, the leader of one faction of the so-called Sinaloa cartel.
The police official lost that battle.
In the days since he was gunned down, officials have revealed that Millan Gomez's killers probably knew that he slept in more than one home. They even had the keys to his front door, a stunning illustration of the cartels' power to gather intelligence about government operations.
Officials and analysts argue that the assassination was actually a sign of weakness. Pressured by the government, they say, the Sinaloa cartel is in retreat and disarray, split into factions that have turned on each other. Several mid- and high-ranking members of the gang have been arrested, and army troops already deployed in the region have seized drug shipments, destroyed opium poppy fields and seized more than 100 airplanes believed to be used by traffickers.
Killing Mexico's No. 3 public-safety official was a reckless act committed by cornered criminals, the government says.
"We have damaged their financial and logistical operations," Calderon said Monday. "And this has apparently provoked these criminal acts of desperation in which they seek to recover the protected spaces they've lost."
Millan Gomez, who coordinated joint efforts of the army and federal police, had struck several blows against the Sinaloa cartel. The biggest was the seizure of 23 tons of cocaine in October at the Pacific port of Manzanillo.
But the investigation into Millan Gomez's killing has also revealed the power and reach of the cartel.
In Mexico City, Millan Gomez's bodyguards and several of his aides have been forced to take polygraph examinations. Investigators believe a top official close to Millan Gomez must have betrayed him to cartel hit men.
At least one federal police officer has been arrested in the killing: Jose Antonio Montes Garfias, a 14-year veteran assigned to the regional headquarters of the federal police in Culiacan, the capital of Sinaloa state.
Details also have emerged on the extent to which Mexico's drug organizations rely on former army soldiers and serving policemen.
The Sinaloa cartel is one of the oldest in Mexico. Founded by a few close-knit families and once dominant in Mexico's drug trade, it has been challenged over the last decade by the so-called Gulf cartel, based in the northeastern border state of Tamaulipas. But the Sinaloa traffickers still control Pacific smuggling routes that U.S. officials say have become the most popular for shipment of Colombian cocaine to the United States.
Joaquin "Shorty" Guzman, the fugitive leader of the gang, is fighting for control of the group with his former top henchman, Beltran Leyva, officials say. The animosity between the factions may have led to the killing of Guzman's son, Edgar, on May 8, the day Millan Gomez was slain.
Millan Gomez was directing an operation against Beltran Leyva just hours before he was killed, officials said. His police officers had cornered the drug baron on a highway outside Cuernavaca, south of Mexico City. But they found themselves outgunned by a well-coordinated team of bodyguards, led by several former members of the 43rd Infantry Battalion of the Mexican army.
Two men on each side were killed, authorities said. Nine of Beltran Leyva's bodyguards were arrested.
But Beltran Leyva escaped. That evening, his plan to rid himself of the tenacious Millan Gomez moved toward fruition, authorities said. According to federal police, the cartel leader contracted Millan Gomez's killing to a criminal gang in Mexico City.
Millan Gomez's schedule was a closely guarded secret, known only to a few associates, officials said. But as he headed home accompanied by two bodyguards in an armored sport utility vehicle, four cartel hit men were waiting behind his front door.
The bodyguards dropped off Millan Gomez, who entered his home alone. Seconds later, they heard gunshots.
Though wounded by at least eight shots, Millan Gomez was able to grab one of the attackers, officials said.
"Who sent you?" he demanded. "Who sent you to kill me?" He died at a hospital, the third high-ranking federal police official killed in Mexico City in a week.
His bodyguards were wounded in an exchange of gunfire with the fleeing assailants. One man, a petty criminal with two convictions for auto theft, was arrested. At least three escaped.
Several analysts said Mexico was entering a new phase of the drug war. The government offensive, they said, had caused cash shortages and splits in the cartels.
Newspaper columnist Jorge Fernandez Menendez compared the Mexican traffickers' predicament with that of Colombian drug lord Pablo Escobar and his Medellin cartel during its decline in the late 1980s and early 1990s.
"The weaker Escobar became, the more enemies he made . . . and the less money he had, the more he resorted to violence to take revenge on his enemies and strike fear in them," Fernandez Menendez wrote in the newspaper Excelsior.
On Tuesday, Calderon's "security cabinet," including the Interior and Defense secretaries and attorney general, made a point of traveling to Sinaloa's capital for a meeting. Then, the troops were dispatched.
"If necessary, we'll bring even more troops," Defense Secretary Guillermo Galvan said. "Organized crime is not, and can never be, stronger than Mexico."
Officials quickly moved to close 20 of the 22 currency exchange houses in Culiacan and audit their operations. Such businesses often are used by traffickers to launder profits.
The drug traffickers responded with the guerrilla-style attack against the police station.
On Wednesday, as many as 40 cartel operatives launched an attack on a police station in Guamuchil, a city 60 miles northwest of Culiacan. They came in 10 late-model pickups, and wore jackets bearing the logo of a federal police agency.
As the half a dozen police officers inside scrambled for cover, the attackers sprayed the building with automatic-weapons fire and set off at least two grenades. Two officers were hurt before the attackers fled, leaving behind several hundred spent ammunition casings.
The traffickers have also posted signs on Culiacan street corners that taunt the government efforts.
"Little soldiers of lead, generals of straw," read one sign, painted on a sheet.
"This is the territory of Arturo Beltran."