April 16, 2011 - Mexican authorities announce the arrest of Martin Omar Estrada Luna -- nicknamed "El Kilo", a presumed leader of the Los Zetas drug cartel in San Fernando. Estrada Luna has been identified by authorities as one of three prime suspects behind the mass graves discovered earlier in April 2011.
April 29, 2011 - Former drug cartel leader Benjamin Arellano Felix is extradited to the United States.
May 8, 2011 - Twelve suspected members of the Los Zetas drug cartel and a member of Mexico's Navy are killed in a shootout on a Falcon Lake island, after troops patrolling the area spot a camping area on the island. The suspected drug traffickers were storing marijuana on the island to be transported by boat to the U.S., authorities said in a statement.
May 29, 2011 - In Hidalgo, ten police officers, including a police chief, are arrested on charges of protecting the Los Zetas drug cartel.
June 14, 2011 - A congressional report shows that more than 70% of firearms seized by Mexican authorities, and submitted to the ATF for tracing, are shown to have originated in the United States. The report covers 29,284 firearms submitted in 2009 and 2010.
June 21, 2011 - Mexican federal police capture Jose de Jesus Mendez Vargas, also known as "The Monkey", the alleged head of La Familia Michoacana cartel in Augascalientes.
July 3, 2011 - Mexican authorities arrest Jesus Enrique Rejon Aguilar, known as "El Mamito," a reported founding member of the Los Zetas Cartel and allegedly connected to ICE Agent Jaime Zapata's death.
July 11, 2011 - The U.S. government announces a plan to require gun dealers in California, Arizona, New Mexico and Texas to report the sales of semiautomatic rifles under certain conditions in an effort to stem the flow of guns to Mexican drug cartels.
July 27, 2011 - Edgar Jimenez Lugo, known as "El Ponchis" or "The Cloak", a 14-year-old American citizen with suspected drug cartel ties, is found guilty of beheading at least four people and sentenced to the maximum for a juvenile, three years in a Mexican correctional facility.
July 30, 2011 - Mexican authorities announce they have Jose Antonio Acosta Hernandez, or "El Diego," in custody. He is the purported leader of La Linea, the suspected armed branch of the Juarez drug cartel, and considered responsible for the death of U.S. Consulate employee Lesley Enriquez and her husband Arthur Redelfs.
August 1, 2011 - Mexican federal police arrest Moises Montero Alvarez, known as "The Korean," a suspected leader of the Independent Cartel of Acapulco (CIDA) and allegedly connected with the murders of 20 Mexican tourists in 2010.
August 25, 2011 - At least 52 people are killed in an attack on the Casino Royale in Monterrey, Mexico. Witnesses told investigators that up to six people entered the Casino Royale and demanded money from the manager, according to Adrian de la Garza, the state attorney general for Nuevo Leon. When the manager refused to pay they set the building on fire, he said.
August 30, 2011 - Mexican officials allege that the five suspects arrested in connection with the Mexico casino fire are members of the Los Zetas drug cartel and had targeted the owners of the casino for not complying with extortion demands. The suspects were identified as Luis Carlos Carrazco Espinosa; Javier Alonso Martinez Morales, alias "el Javo"; Jonathan Jahir Reyna Gutierrez; Juan Angel Leal Flores; and Julio Tadeo Berrones, alias "El Julio Rayas."
September 1, 2011 - A Nuevo Leon state police officer, Miguel Angel Barraza Escamilla, is arrested in connection with the casino fire that killed 52 people in Monterrey.
September 13, 2011 - A murdered man and woman are found hanging from a bridge in Nuevo Laredo. Near their mutilated bodies is a sign saying they were killed for denouncing drug cartel activities on a social media site. The sign also threatens to kill others who post "funny things on the internet."
September 20, 2011 - At least 35 bodies are dumped in a roadway in the coastal state of Veracruz, during rush-hour.
September 23, 2011 - Mexican authorities find another 11 bodies in locations throughout Veracruz.
September 27, 2011 - Five severed heads are found in a sack near an elementary school in Acapulco.
October 4, 2011 - The U.S. Drug Enforcement Administration (DEA) estimates that almost 43,000 people have died in Mexico's drug war since Mexican president Felipe Calderon took office in December 2006.
October 6, 2011 - In an online video purporting to be from the Anonymous hacking group, a masked man threatens to release information about the Los Zetas drug cartel for allegedly kidnapping an Anonymous member.
October 7, 2011 - The Mexican navy announces that it has arrested eight people suspected of involvement in the deaths of 67 people in Veracruz in recent weeks.
October 12, 2011 - A suspected top Los Zetas drug cartel leader, Carlos Oliva Castillo, alias "La rana," or frog, is arrested for allegedly ordering the attack and arson at the casino that killed 52.
November 24, 2011 - Mexican authorities find 26 bodies inside three abandoned vehicles in Guadalajara, Mexico, one day after authorities in Sinaloa state found 16 charred bodies inside two trucks that had been set ablaze.
January 4, 2012 - Benjamin Arellano Felix, a former leader of Mexico's Tijuana drug cartel, pleads guilty to charges of racketeering and conspiracy to launder money. The plea deal calls for the forfeiture of $100 million to the U.S. and a maximum of 25 years in prison.
January 11, 2012 - The office of Mexico's Attorney General releases a statement saying that nearly 13,000 people were killed in drug violence between January and September 2011. This pushes the death toll from December 2006 to September 2011 to a minimum of 47,000 people killed.