Since 2006 the conflict intensified as Mexican authorities stepped up their fight against these cartels .
The Mexico - US border area is the main battleground in the war among drug cartels for control of smuggling routes leading from Mexico to the US .
Since 2006 the conflict intensified as Mexico authorities stepped up their fight against these cartels .
The Mexico - US border area is the main battleground in the war among drug cartels for control of smuggling routes leading from Mexico to the US .