MS-13 has been a frequent talking point of the Trump administration as part of its justification for hard-line immigration policies and border security. It was in that context that Trump brought up MS-13 in his opening statement in a joint news conference with Colombian President Juan Manuel Santos -- as he talked about stopping trans-border crime.
"MS-13, likewise, a horrible, horrible large group of gangs that have been let into country over a fairly short period of time are being decimated by the Border Patrol and by ICE and by our incredible local police forces and they are getting out of our country or in some cases, going directly into prisons throughout our country," Trump said. "But they've literally taken over towns and cities of the United States."
Trump's comments contained a number of mischaracterizations of MS-13 or assertions that are not backed up by any statistics.
While Colombia is an important front in the fight against gangs and drugs, MS-13 is a Central American and US-based gang, so Trump's mention of the issue seemed unrelated to his conversation with Santos.
It was also entirely unclear which cities and town Trump meant were "literally taken over" by MS-13, which remains a small fraction of the overall gang problem in the US, per available statistics.
Neither the Department of Justice, Department of Homeland Security, Immigration and Customs Enforcement nor the White House responded to a request for clarification.
Origin of MS-13: Not imported and not new
Mara Salvatrucha, known as MS-13, is a transnational gang with a heavy presence in Central America -- but it actually began in the United States three decades ago.
MS-13 began in Los Angeles in the 1980s amid a flood of Salvadorans fleeing a civil war to the US.
It was the US deporting these immigrants in the '90s back to Central America that sent the gang there, where it took hold.
Now the gang has footholds in the US and in Central America in cities like Los Angeles, New York and the Washington, DC, region and countries like El Salvador, Guatemala and Honduras.
While it's unknown how much of the Central American strength of MS-13 was homegrown, a Congressional Research Service analysis of MS-13 found
that its ranks were continuously strengthened by deportees from the US returning home, even as members also migrated to the US.
There were roughly 24,000 MS-13 members in Central America in 2012, according to an analysis
by the UN Office on Drugs and Crime. Today, the Justice Department estimates roughly 30,000 members worldwide and more than 10,000 in the US, a number that has held steady for some years but that the department believes is trending upward.
The Obama administration Treasury Department in 2012 sanctioned
the gang as a transnational criminal organization -- the first such designation for a street gang.
Connection to immigration: Difficult to assess
The departments of Justice and Homeland Security have been unable to provide reporters with any estimates of how many MS-13 members nationwide came into the US illegally -- and how many members joined the gang after coming to the US. The gang actively recruits in immigrant communities in the US and often victimizes undocumented immigrants, who are vulnerable to extortion because they fear law enforcement will discover their status.
There are roughly 11 million undocumented immigrants in the US.
The Department of Justice says it has found in recent investigations that gang leaders in El Salvador are directing US cliques to become more violent. It also believes that these leaders have been sending emissaries into the US illegally to connect with local cliques.
Recent MS-13 arrests offer some insight.
ICE last week announced the results of a nationwide anti-gang operation, an exercise the agency has done roughly annually for many years.
Of the roughly 1,300 anti-gang arrests nationwide, 104 individuals were linked to MS-13.
Of those 104, five were US citizens, three were immigrants who were lawfully present in the US and 96 were in the US illegally, according to ICE.
On Wednesday, the Department of Justice announced a major racketeering case against MS-13 ring leaders in Los Angeles. Of the 44 people charged, the assistant US attorney in the case said more than half were undocumented.
In a case out of Queens, New York, last week, only one out of three defendants charged was in the US illegally.
Reach in the US: Fraction of total gang problem
MS-13 is active in 40 states plus the District of Columbia, the Department of Justice estimates. Combating the gang has been a focus of law enforcement for decades, and DOJ says that great strides were made in disrupting the gang in 2009 and 2010.
There is no hard evidence that MS-13 has become more of a problem in the US in recent years. Arrests of gang members by Homeland Security Investigations under ICE have fluctuated in recent years, but have shown no clear downward or upward trend. Anecdotally, some local law enforcement chiefs have noticed an increase in murders connected to the gang in some capacity in recent months.
Per the FBI's most recent statistics
, the roughly 10,000 MS-13 members are a fraction of the estimated 1.4 million members of US gangs nationally, and made up less than 10% of the arrests in ICE's gang crackdown announced last week.
In terms of number of arrests, MS-13 lagged behind the number of members of Bloods and Sureños arrested and was equal to the number of Crips. Another roughly 600 confirmed gang arrests did not belong to any of those gangs.