1) Before 2006, drug cartels operated with impunity in Mexico, bribing and threatening police forces. 2) In 2006, newly elected President Felipe Calderon launched a military crackdown on the cartels, starting the Mexican Drug War. 3) In early 2007, thousands of soldiers were sent to Tijuana to arrest drug dealers, leading to a shootout where hostages died in the crossfire. The campaign upset citizens who got caught in the violence.