CIUDAD JUAREZ, Mexico, (Reuters) – One man looms behind the worst violence in a drugs war on Mexico’s U.S. border that is shaking President Felipe Calderon’s government and worrying Washington.

Joaquin Guzman, known as “Shorty” at just 5 feet tall (1.55 meters), is Mexico’s most wanted man and set off a wave of killings in the border city of Ciudad Juarez early last year when he tried to muscle in on the territory of a local cartel.
A turf battle between Guzman’s enforcers from the Sinaloa cartel and local Ciudad Juarez drug runners has since killed more than 2,000 people here and forced the government to deploy 7,500 troops and federal police to take control of the city.
Guzman, 51, has avoided capture several times since he escaped from a high security jail in a laundry van in 2001.
Mexican anti-drug officials say he began waging war for Ciudad Juarez when the local cartel tried to charge him taxes for smuggling narcotics through the city into Texas.
“Guzman has been pouring hitmen and resources into the city since last year to try to eliminate the Juarez cartel,” said Tony Payan, a drug-trade analyst at the University of Texas in El Paso. “He has not been able to dislodge them,” he added. The killings have turned Ciudad Juarez into the most violent city in Mexico, where more than 6,000 people died in drug warfare last year.
Guzman, who officials believe changes his cell phone every day to avoid being tracked, is also fighting for control of the lucrative smuggling route through Tijuana into California, turning the city into one of Mexico’s most bloody.
He set off a similar fight for smuggling routes into eastern Texas in 2006 but has so far been driven back by the rival Gulf cartel that has long controlled the area.
U.S. and Mexican authorities say Guzman has also been weakened by a break-up of factions within his cartel because of internal conflicts, and pressure by Mexico’s military.
But he appears far from defeated.
“He is the silent shadow across Mexico. He is everywhere,” said a senior Mexican military official in Ciudad Juarez who declined to be named.
Guzman is unlikely to be in Ciudad Juarez himself and state prosecutors say the hundreds of bodies that have come through the city’s morgue are mainly cartel foot soldiers and police.