The details of the agreement between Comba and the DEA may never be known. But the terms were obviously favorable enough for Comba to leave Argentina, where it appears the negotiations took place, and go to the Caribbean island of Aruba. There he surrendered to DEA agents and was flown to New York, according to press reports.

Comba is not the first top Colombian drug trafficker to voluntarily surrender to US authorities, and he is unlikely to be the last. Carlos Mario Aguilar, alias "Rogelio," seen as the heir apparent of the "Oficina de Envigado," delivered himself to face US Justice in 2008, again via Argentina, leaving a vacuum in the Medellin mafia.

Comba headed the Rastrojos, one of Colombia's most powerful transnational criminal organizations (TCO's), founded in 2002 as an armed wing of one of the factions of the Norte Del Valle Cartel.

[See InSight Crime's profile of the Rastrojos]

The group has rapidly expanded since 2008, when Comba took over the organization after killing his boss -- and Rastrojos' founder -- Wilber Varela, in Venezuela. Comba's play to take over the criminal group was backed by the Rastrojos' military leader, Diego Perez Henao, alias "Diego Rastrojo," and another one of Colombia's most powerful traffickers, Daniel Barrera, alias "El Loco." The alliance with Loco Barrera allowed the Rastrojos to move away from their traditional base along the Pacific coast, and consolidate territory on the other side of the country, on the frontier with Venezuela. They now have presence in at least 13 of Colombia's 32 departments.

However, Comba quickly moved up the list of priorities for both US and Colombian law enforcement as his power and influence grew. Working with the Colombian police, the DEA began to target "Los Combas," a faction of the Rastrojos led by Comba and his brothers. A series of arrests of key Los Combas operatives not only weakened Comba himself, but the influence of the Rastrojos. In June 2011, Carlos Hugo Garcia, alias "Chocolate," was captured. He supervised Los Combas enforcers and assassins, based in Cali. His arrest was so damaging that the Rastrojos planned to break him out of prison, although details of the operation were leaked to authorities and Garcia was moved. Then in March 2012, Comba's brother, Juan Carlos Calle Serna, alias "Armando," was captured in Ecuador.

These arrests, along with persistent rumors that Comba was negotiating with US authorities, created turmoil within the organization. Comba's authority had initially been challenged by outsiders, the most prominent among them Victor Patiño Fomeque and Martin Fernando Varon, alias "Martin Bala." Both men have their roots in the now extinct Cali Cartel. Patiño has a personal score to settle with Comba after some 30 members of his family were murdered in a failed attempt to stop him cooperating with US Justice. Martin Bala runs a drug trafficking operation with tentacles into Spain.

Comba saw his expansion plans hindered as early as 2009, as the rival network of the Urabeños began to support his rivals and sought to challenge Rastrojos power in key part of the country. The war between the Rastrojos and Urabeños was most fierce in the area of Bajo Cauca, on the frontier between the provinces of Antioquia and Cordoba. Comba began to lose ground here in the face of Urabeños offensives, and then saw his key commander in the region, Angel de Jesus Pacheco, alias "Sebastian," killed by his own bodyguards in July 2011. Comba was then forced to negotiate a truce with the Urabeños, withdrawing the Rastrojos from parts of Bajo Cauca, in return for the Urabeños withdrawing their support for Patiño and Martin Bala.

These reverses, and the persistent rumors that Comba was negotiating with the US, which began to leak in August last year, led elements within the Rastrojos to question the existing leadership. The natural successor to the leadership of the Rastrojos is "Diego Rastrojo," and there are already indications that he has made a move to take over the group's operations, with the killing of a senior Comba associate in the crucial border city of Cucuta, the gateway to Venezuela. Diego Rastrojo has long commanded much of the Rastrojos' rural troops (estimated to be over 1000 fighters), protected drug laboratories, and controlled access to coca crops. There is no other leader with his military muscle and contacts to mount a serious bid to head the Rastrojos.

However it is in Cali, the home of Los Combas, that is likely to be the centre of any power struggle within the Rastrojos. Police in Cali are already on a heightened state of alert, braced for a new wave of killings among the city's mafia.

It is unclear whether the truce negotiated with the Urabeños will survive the surrender of Comba. The Urabeños will almost certainly try to take advantage of the inevitable chaos within Rastrojos ranks. They are already known to be pressuring the Rastrojos along the Venezuelan border, and expanding into Colombia's eastern plains, threatening the interests of Comba's one-time ally, Loco Barrera.

While the surrender of Comba will certainly create problems for the Rastrojos, it will not signal their demise. The group does not act as a hierarchical and structured organization, but rather a network of criminal enterprises linked by the same franchise name. Cocaine will continue to flow from Colombia with little interruption.