On Jan. 3, 2007, Calderon donned a military-green jacket and cap while reviewing progress of the Michoacan campaign in the city of Apatzingan, an image that came to symbolize a looming militarization of Mexico's struggle against drug gangs.
There was never a formal declaration of war, and the start of the conflict itself is a matter of dispute, as it was with Calderon's predecessor, Vicente Fox, who first sent soldiers to tackle cartels.
But in mid-2007, Calderon used the term "war" freely in two speeches to describe his government's efforts. In Guadalajara, he said he was carrying out a "frontal war" against criminals. In Monterrey, he called it a "long-term war."
As casualties mounted, Calderon's language about the conflict evolved. In May 2011, he told Mexican migrants in New York that "it's not a war against narco-traffickers as such." In recent years, he began urging citizens, foreigners and even journalists to "speak good about Mexico" to outsiders.
Violence in Ciudad Juarez
A sharp increase in homicides registered in January 2008 in Ciudad Juarez signaled the start of the cruelest sub-conflict in Mexico's drug war, the battle for control of Juarez's crucial port with the United States, which led to an estimated 10,000 dead.
Businesses were victims of extortion, and owners were brutally gunned down if they refused to pay. Hospitals, even schools, were targets. The violence led to an exodus from the city to El Paso across the Texas border, or to other cities in Mexico. The violence included beheadings, mass executions and bodies hanging from bridges, atrocities that also were seen in Michoacan, Guerrero, Nuevo Leon, Veracruz and elsewhere.
Analysts say the Juarez cartel finally succumbed to the onslaught brought by the Sinaloa federation, with homicide rates dropping this year. However, corruption among federal police and military personnel operating in the area is considered rampant. Human rights abuse claims against authorities ballooned in Ciudad Juarez and the rest of Chihuahua during Calderon's term.
The Villas de Salvarcar massacre occurred on Jan. 30, 2010, when Luz Maria Davila's teenage sons, Marcos and Jose Luis, were killed. She still lives in Juarez with her husband and continues to work at a factory on the border.
"In that moment, I felt like no one was listening to me," Davila said, recalling her confrontation with Calderon in a later interview.
Police director assassinated
In May 2008, Edgar Millan Gomez, the acting director of what was then called the Federal Preventive Police, was shot and killed in his Mexico City apartment by gunmen waiting inside. His slaying was allegedly a retaliation strike by a branch of the Sinaloa cartel.
Michoacan grenade attack
On Sept. 15, 2008, the night before Independence Day, an assailant threw a hand grenade into throngs of people gathered at the main plaza in the Michoacan capital, Morelia, killing seven. The attack was dubbed an act of "narco-terror" and blamed on the local cartel La Familia Michoacana.
Suspicion after crash
On Nov. 4, 2008, as Barack Obama was elected president in the United States, a Learjet carrying Mexico's second-in-command and a top former prosecutor against organized crime crashed in rush-hour traffic near Chapultepec Park, killing 16 people in total.
The death of Interior Secretary Juan Camilo Mouriño, 37, noticeably shook Calderon, who had called him a close friend. Another passenger was Jose Luis Santiago Vasconcelos, a respected former attorney general who had received death threats.
Government investigators ruled the crash an accident, but popular suspicion remained that the plane was deliberately brought down. Investigative journalists in Mexico explored potential scenarios of an attack linked to organized crime or internal struggles in Mexico's political right.
Tamaulipas candidate killed
Days before a July 2010 election, the candidate for governor of Tamaulipas and four campaign aides were killed in a highway ambush.