Comuna 13 is the most violent neighborhood in the embattled city of Medellin. And with the powerful Urabeños criminal gang edging in on territory long controlled by the city's feared mafia, there is little sign of peace on the horizon.

Last year the neighborhood saw 162 murders for every 100,000 people. The violence comes amidst a nationwide spasm, in which Colombia's large criminal organizations are splintering or trying to consolidate gains made at the expense of others, while the government attempts to catch up with these developments. Within this, InSight takes a close look at Medellin.

The city has long been a bellweather for measuring violence and criminal activity in Colombia, and Comuna 13 has been at the heart of the storm. For years, criminal groups -- from street gangs to leftist rebels to drug trafficking organizations -- have made this area their home.

As in other parts of the country, geography plays a role. In this case, the hills make the district a natural fortress, difficult for government forces to penetrate and control. As police patrols make their way up the winding streets, it is all too easy for lookouts to spot them and retreat to safer ground, along with their stashes of arms and drugs.

On one street corner in San Javier barrio, the lookout post for the local gang, the Picubas, is in a square concrete house with a clear view of the neighborhood soccer pitch, the police station, the military post, and the road leading to the metro station. The former occupant of the house, a woman, was reportedly driven out after she tried to tip off the police about gang activity.

The "sapa," or tattletale, moved out, one of the estimated 70 households displaced from Comuna 13 so far this year, and the Picubas moved in and set up shop. Every proper combo has their own lookout post, as well as a "casa de vicio" -- where drugs are sold -- and sometimes, a torture house, where the "sapos" who do not leave willingly are taken.

Such is life in Comuna 13, population 134,000, where police have registered 95 murders so far this year. In 2010, this was the most violent neighborhood in Medellin, where 243 out of the city's 2,019 homicides took place.

In many ways, the urban war in Comuna 13 reflects the same battle playing out in other hotly contested drug "plazas" across the region -- the states of Nuevo Leon and Tamaulipas in Mexico, or the municipality of Caucasia in Colombia. Here, the multiplicity of competing gangs has created a situation of "disorganized" crime. Instead of doing what's good for business -- keeping murder rates low and police attention to a minimum -- the criminal world is in turmoil and in need of an arbitrator to re-establish authority.

Like Mexico, where the splintering of authority has led to the creation of smaller but no less violent groups like the Cartel of Acapulco and Mano Con Ojos, Colombian gangs are struggling to establish themselves in this new criminal hierarchy. And peripheral slums long ignored by the state -- Medellin's Comuna 13, or Ciudad Juarez's Rivera del Bravo -- are the perfect launching pad. In these neighborhoods, traffickers have found a ready pool of recruits and potential drug users, as well as useful corridors for smuggling drugs and arms.

In Comuna 13, much of the violence is about controlling the San Juan highway, which leads out of the city to northern Antioquia and the Uraba coast. Those who control the highway decide what enters and leaves the city: drugs, guns, money. Asking who controls Comuna 13 means asking who controls the San Juan, and since the days of Pablo Escobar in the 1980s, the highway has been Medellin's prime mover of illegal product. The armed group set up by Escobar, now known as the Oficina de Envigado, is still the biggest criminal organization in Medellin. But it has split into rival factions, and neither side has yet been able to muscle their way into Comuna 13 and the San Juan.

The Oficina Wars

The current war in the Comuna is being fought between two rival factions of the Oficina de Envigado: one side led by Maximiliano Bonilla, alias "Valenciano," rumored to be based on the Caribbean coast; the other led by Erick Vargas Cardenas, alias "Sebastian," who reportedly moved from the countryside back into the city last August, in order to take a personal role in overseeing the city's street battles.

Different factions of the Oficina control different levels of the criminal economy. The most lucrative involves contacts with international cartels. Others include control of the highway, control of big drug shipments, micro-trafficking (or "narcomenudeo"), extortion, legal and illegal casinos, prostitution rings and the networks of sicarios, or hitmen. Fighting for their place in this economy are around 250 street gangs, made up of an estimated 5,000 youths, who outsource their services to either Vargas or Bonilla.

A Medellin-based NGO known as IPC estimates that in Comuna 13 alone there are between 21 to 25 rival gangs. At the moment, the forces of Vargas and Bonilla appear to be in a deadlock. Vargas is believed to control eleven of Comuna 13's barrios, including most of those to the north of the San Javier metro station. Bonilla controls seven, including the key barrio of Antonio Nariño, which the San Juan highway passes through.

The Combos

Breaking down the neighborhoods controlled by the Comuna 13 street gangs, or "combos," is trickier (see map below). The smaller ones often have no more than ten members, and defend a single city block. Besides peddling marijuana and "bazuco" (a cheap variant of crack cocaine), the combos charge each household a weekly fee -- 5,000 to 10,000 pesos ($2.75 to $5), in exchange for providing "security" services. Stores pay more, perhaps up to 30,000 ($15), depending on the business.

Some of the combos, like one controlled by a rumored ex-lover of Bonilla, alias "La Nana," are focused on just one line of business: collecting daily extortion payments from the city's bus companies, of about 30,000 to 40,000 ($22) pesos per driver. Those who don't pay are killed or have their buses attacked and burned: According to IPC, last year 29 drivers and 25 buses gave up their routes through Comuna 13 due to threats.

The larger combos in Comuna 13 include the Picubas, who work for Bonilla, and the Saladeños, reportedly on Vargas' payroll. Neither are believed to have more than 40 members. Much of the current violence in the Comuna is caused by clashes between these two gangs in Las Independencias and Nuevo Conquistadores, where Vargas has deployed the Saladeños to challenge Bonilla's traditional territory. The murder of a young hip-hop artist, which inspired a peace march in late March, was reportedly triggered when he crossed the line dividing Saladeño turf from that of their rivals.

As a result of the gang battles, Comuna 13 saw some of the highest rates of intra-urban displacement last year, with an estimated 1,473 residents forced to leave the neighborhood. Many of these displacements are concentrated in areas where gangs loyal to Vargas are fighting to push out combos allied to Bonilla. To the south of the metro station, these hotspots include 20 de Julio, Las Independencias, Nuevo Conquistadores and El Corazon; to the north, Juan XXXIII and El Socorro.

Urban War

Combo violence in Comuna 13 is nothing new. A book written and published in 1991 by Alonso Salazar, the city's current mayor, describes a gang problem not much different than the one afflicting Medellin today: displaced farmers, forced off their land by armed groups, settle in the outer slums where there is little hope of jobs or even basic services like electricity and water. The younger generation, born of these displaced parents grew up and found work in the criminal organizations run by Escobar and his de facto heir, Diego Fernando Murillo, alias "Don Berna," who understood the power of this social base and harnessed it to his advantage.

What has changed about Comuna 13 since Escobar's time is that the guerrillia militias are largely gone. Medellin was the first major city in Colombia to see urban militias appearing in the hillside slums: first the National Liberation Army (Ejercito Nacional de Liberacion - ELN), followed by the Movimiento 19 de Abril (M-19). Another left-wing vigilante group, the People's Armed Command (Comandos Armados del Pueblo - CAP) first made their presence felt in Comuna 13 in 1996. In contrast to Comuna 13's street gangs, the CAP gave their recruits military training and pushed their leftist politics. They patrolled the streets, solved quarrels between neighbors, and funded themselves by collecting "security" payments from bus companies and stores.

The left-wing militias were not the only vigilante groups to emerge. The so-called CONVIVIR, a security co-op promoted by then-governor Alvaro Uribe, was active in Medellin during the 1990s. That same year saw the creation of paramilitary group Bloque Metro, which aimed to take the fight against the guerrillas from the Antioquia countryside into Medellin.

By 2000, the Revolutionary Armed Forces of Colombia (Fuerzas Armadas Revolucionarias de Colombia - FARC), the ELN and the CAP all had bases in Comuna 13. It would take the security forces -- working alongside the paramilitaries -- a total of 17 operations to drive them out.

The culmination was Operation Orion in 2002, which officially saw 17 people killed, 30 wounded, and close to 400 arrested (only 80 of whom were tried and sentenced to prison). Part of the reason it was so difficult for the government to retake Comuna 13 from the leftist guerrillas was, once again, the hills. The narrow streets, the houses crammed together, the lack of space and the abundance of lookout spots makes Comuna 13 a very easy place to control. This also makes it an ideal spot for urban warfare.

Enter the Urabeños?

The defining characteristic of the conflict in Comuna 13 is the lack of any central authority. After Operation Orion, paramilitary group Bloque Metro was absorbed by the Medellin crimelord Murillo and his paramilitary wing, Bloque Cacique Nutibara. Murillo's control was total, even during a peace process between the government and the paramilitary groups.

In 2003, for instance, in order to keep up the appearance that Murillo was collaborating with authorities during that process, he ordered the combos to keep murder rates low. The peace lasted until Murillo himself was extradited in 2008, and Vargas and Bonilla began battling for control of the city.

With the upper level of the Oficina's command in disarray and under serious pressure from the authorities, the lower level is even more fractured. Most of the combos are not acting with any kind of long-term strategy, besides scrambling to make a living while defending their turf. The smaller the combo, the smaller their territory, and the more important it becomes to defend it with escalating levels of violence.

The long-term risk is that vigilante groups will again arise to establish order on the streets and stop the combos from tearing each other, and the neighborhood, apart. InSight has heard reports that the Urabeños may see themselves in this role.

Since its formation in 2008, the Urabaños have sought to expand their influence in the city. And since 2010, they have reportedly established a cell with an estimated 70 members in the areas of Belencito and Betania.

Their advantage over the combos is money and weapons: They come armed with Galils and R-15 rifles, which overshadow the .38 hanguns and 9 mm pistols favored by the street gangs. If Bonilla falls, an event that was mistakenly reported in recent days, and if Vargas is not able to assert himself as the new "Don Berna," the Urabeños could have a real opening before them.

The other risk is that violence could begin spilling out of Comuna 13 into more peaceful barrios, like Envigado, or even the countryside. This is apparently what happened April 26, when ten people were kidnapped from the rural town of Sopetran, about 20 miles from Medellin -- one source told InSight that Bonilla's men deployed a team of recruiters to work the countryside, and Vargas sent a team of hitmen after them.

Murder rates are also reportedly up in towns outside Medellin like Rionegro and Marinilla, where urban gangs are increasingly deploying recruiters or small-time drug dealers, seeking any edge possible over their city-based rivals.

Another fear is that the FARC, increasingly battered in the countryside, could again see an opening in Medellin. One way that a combo could gain an undisputed edge over a rival group is through learning military training and discipline -- a service that the FARC and the ELN once provided to disaffected youths.

But re-entering Comuna 13 will not be easy for any leftist militia. In barrio San Javier, visible from the Picubas' lookout post is a white house in ruins. This, reportedly, was once a stash house for FARC weapons; Bonilla allegedly had it dynamited during the chaos of Operation Orion. Nearly ten years later, nobody goes near it.