(CNN) -- Mexico's war against the drug cartels is frustrated by a risk-averse army and interagency rivalries, according to U.S. diplomatic cables obtained by WikiLeaks. But amid some downbeat assessments of the challenges faced by President Felipe Calderon, some of the cables celebrate outstanding successes against the cartel "capos."
One such success came almost exactly a year ago, when a Mexican naval unit killed one of Mexico's leading cartel figures, Arturo Beltran Leyva -- with plenty of assistance from the United States.
"The arrest operation targeting ABL began about a week prior to his death when the Embassy relayed detailed information on his location to SEMAR [Mexican Navy]," according to a cable sent soon after the operation.
The naval unit "raided an identified location, where they killed several ABL bodyguards and arrested over 23 associates, while ABL and Hector [his brother] escaped."
But time was running out for Beltran Leyva (also known as El Fantasma and El Elegante), thanks to U.S. surveillance.
The cable continues: "the Embassy interagency linked ABL to an apartment building located in Cuernavaca (about an hour south of Mexico City), where ABL was in hiding.... ABL's forces fired on the SEMAR operatives and engaged in a sustained firefight that wounded three SEMAR marines and possibly killed one."
Besides Beltran Leyva, at least three other cartel operatives were killed during the Dec. 16, 2009, raid, with a fourth committing suicide.
The success of the operation was especially pleasing to the United States because its military had spent years training Mexican naval units.
Some might question why the navy was involved in a land operation.
This and other cables provide the answer: The army had declined to act quickly on information about Beltran Leyva's whereabouts and is described as "risk averse."
After the Beltran Leyva operation, there was glowing praise from U.S. diplomats for Mexican navy units.
"SEMAR is well-trained, well-equipped, and has shown itself capable of responding quickly to actionable intelligence," a cable read. "Success puts the Army in the difficult position of explaining why it has been reluctant to act on good intelligence and conduct operations against high-level targets."
There is no euphoria about Beltran Leyva's demise, but the embassy hopes it will mark a new beginning. "His death will not solve Mexico's drug problem, but it will hopefully generate the momentum necessary to make sustained progress against other drug trafficking organizations."
Since Beltran Leyva's death, Mexican security forces have scored some significant successes in arresting or killing leading cartel members, and often SEMAR units have been in the vanguard. Last month the Navy Ministry confirmed its forces shot and killed Ezequiel Cardenas Guillen, alias "Tony Tormenta," one of the top members of the Gulf cartel.
And, in January this year, there seemed to be optimism that some of the institutional challenges were at last being tackled.
"A truly joint effort to implement a new U.S.-Mexico strategy is yielding stronger organizational structures and interagency cooperation on both sides and a deeper understanding of the threat posed by the drug trafficking organizations," reads one cable.
The same cable noted that the Mexican Army [SEDENA] had for the first time asked the United States for special forces training. "We need to capitalize on these cracks in the door. Any retreat on engagement on our side will only reinforce SEDENA's instincts to revert to a closed and unaccountable institution."