 Although violence between drug cartels has been occurring long before the war began, the government used its police forces in the 1990s and early first decade of the 21st century with little effect.That changed on December 11, 2006, when newly elected President Felipe Calderón sent 6,500 federal troops to the state of Michoacán to put an end to drug violence there.This action is regarded as the first major retaliation made against cartel operations, and is generally viewed as the starting point of the war between the government and the drug cartels.