Joaquín "El Chapo" Guzmán was captured thanks to a satellite phone that he used last Monday to call one of his subordinates and ask him for help to escape Culiacan where he was hiding in a tunnel. El Chapo's capture represents the biggest police successes in the last decade, and it had its beginnings in the capture of Daniel Fernández Domínguez "El Pelacas", arrested on the 12th of February in Puebla in a joint effort between the CIA and the Mexican Attorney General's office. 

Dominguez, originally from Monterrey, had spoken with Guzmán and Ismael "El Mayo" Zambada not long before his arrest. He had 20 different cell phones at the time of his capture: several of them had calls to numbers with a Sinaloa area code. Following some rapid investigation, the CIA determined that among the many numbers in the phone, were the phone numbers for Joel Enrique Sandoval Romero, "El 19", his brothers Apolonio "El 30" and Cristo Omar "El Cristo", Jesús Andrés Corrales Aztorga "El Bimbo" and Mario Miguel Pérez Urrea "El Pitaya".

With this information, the next day the CIA and Marines entered the municipality of Reforma in Sinaloa, where Joel Sandoval was captured along with his accomplices. The operatives had formed a map of links created with phone data, license plates, restaurants and photographs that the sons of the drug dealers had uploaded to social media. The capture of Sandoval was key as one of the numbers registered in his phone, he assured the operatives, belonged to Chapo himself.

The other key piece of information obtained by the DEA this last weekend was that "El Chapo" and his colleage, "El Mayo" Zambada were planning a meeting in Culiacan, although the exact place had not been determined. A number of radio conversations in Culiacan made reference to this meeting, without specifically naming the time and place. 

One of the main obstacles facing Mexican authorities was that Guzman was using a satellite phone. However, with technical support from the DEA, they were able to locate Guzman using the latest geographic locating technology. Last Monday, the same day as "El  19" was captured, the DEA and Mexican authorities tracked the signal. From that moment on, US authorities worked in conjunction with Mexican officials. Both governments still feared that El Chapo might just dispose of his phone. 

When the device was first located, it was turned off. However, after few hours, the cell phone was turned on ad a call was made. It was Guzmán asking for help to escape Culiacán, where he was hiding in a tunnel. The voice was identified as El Chapo's. From that moment, the Marines practically surrounded the Sinaloan capital. The phone led operatives to a home in the Colonia Libertad suburb, where CIA agents found tunnels hidden under bath tubs. However, the cartel leader had escaped. 

Authorities detected his [hone being turned on and off at various times throughout the day as El Chapo used it only to make calls. That same day, the device's signal was located in Mazatlán. The government waited several days to track and study the phone's movements, as well as studying the security circles surrounding El Chapo, among which were local police officers in the seaside town. 

"If we had sought to capture the objective directly on Monday or the day before, the only thing we would have achieved would have been that El Chapo would've escaped in a gunfight. To not miss him, we had to study those that were in his security network and police officers on his payroll," said an officer involved in the operation. "He was followed throuhout the week: we closed in on him and determined a plan of action."

The CIA observed that El Chapo drove a sand-colored Cherokee with a high-level of bullet proofing, much like the vehicles used by the American embassy in Mexico. He was discreet and not followed by any bodyguards. They also determined that his chief bodyguard was Carlos Manuel Hoo, who accompanied him day and night. Early on Saturday morning, Special Armed Forces entered a building in Mriamar, on Avenida del Mar 608, in the Colonia Tellería neighborhood. Upon entering, they captured Hoo, who led them to the fourth floor. At  6:40 AM, marines entered apartment 401 and captured Guzmán Loera.