T he Mara Salvatrucha (MS-13) is a violent criminal gang operating both in the United States and abroad—namely Central America. U.S.-based members have committed both local and transnational crimes ranging from extortion, homicide, and drug distribution to human and drug trafficking. The gang has a reputation for committing particularly violent crimes, which has generated attention from law enforcement, policymakers, and the public. This report provides a brief background on MS-13 with a focus on its structure and criminal activities in the United States. It highlights U.S. law enforcement initiatives and other federal resources used to counter the gang's illicit activities. It discusses how the gang is conceptualized by the federal government and how this conceptualization may drive specific policy responses to the gang's activities. The report also provides an overview of selected domestic policy issues Congress may examine as part of its efforts to counter MS-13. MS-13 was born on the streets of Los Angeles, CA. It was formed in the 1980s by refugees who were fleeing civil conflict in El Salvador. When these Salvadoran nationals moved into the Los Angeles area, some youth coalesced to form MS-13, in part for protection from existing Latino gangs, such as the 18 th Street gang, as well as for a way to connect with other Salvadorans. By the 1990s, MS-13 had reached the East Coast, particularly Washington, DC, and Long Island, NY. Historically, MS-13 members were mostly Salvadoran nationals or first-generation Salvadoran-Americans, but the group has expanded to include other Central and South American immigrants. MS-13 has largely focused on creating an identity and community, though members do engage in activities that generate revenue for the gang. MS-13 became a transnational gang as members who were deported from the United States to Central America established gang ties there. Legislation enacted in the mid-1990s increased the number of foreign nationals subject to detention and removal from the United States. From 2001 to 2010, nearly 130,000 foreign nationals were deported to Central America because of a criminal conviction, primarily to the Northern Triangle countries of El Salvador, Guatemala, and Honduras. The exact number of these deportees who were gang members is unknown, as is the number of deported gang members who were affiliated with MS-13. However, some of these deportees helped to establish MS-13 gang ties in their home countries (where gangs were already present) and assisted in the spread of U.S. gang culture in Central America. In recent years, law enforcement, the media, and policymakers have shown interest in MS-13 and its violent criminal activities. High-profile incidents of violent behavior committed by gang members have raised questions about whether this reflects a developing organizational structure, increasing size, or changing criminality. In the United States, MS-13's organizational structure largely consists of loosely organized cells, or "cliques." These cliques vary in size and in the number that may exist in a particular locale, but each clique typically has ties to a particular territory. Researchers have noted that this territory serves two purposes: (1) it contributes to a clique's sense of neighborhood and community, and serves as a place where they can recruit, and (2) it is an area where the gang generates money from illicit activities such as extortion or charging "rent" on local businesses. In some areas of the country, MS-13 cliques are more organized, and several operate as part of a larger "program." In some instances, in "places where the MS13 is very organized, such as Los Angeles and El Salvador," there may be an additional organizational layer where programs answer to a ruling council. Generally, the U.S. MS-13 structure of relatively diffuse cliques differs from the gang's more organized structure in El Salvador. Some have suggested that MS-13 may try to consolidate its power structure to exert more direction over the U.S. cliques; this has been attempted unsuccessfully at various times, and the extent to which such control may take hold has been debated. In some instances, leaders in El Salvador, including prison-based leaders, have tried to exert more direction over activities of U.S. programs and cliques; however, researchers have indicated that leadership in El Salvador may have little or no direction over activities of the powerful MS-13 programs and cliques in the United States. While some have suggested that the size of MS-13 has grown in the United States, since at least 2005 the FBI has consistently estimated the domestic size of the gang to be around 10,000 members. Of note, it appears that federal law enforcement may be moving away from generating regular estimates of gang membership in the United States, both in aggregate and for specific gangs. For instance, after 2009 the National Gang Threat Assessments ceased including MS-13 membership estimations. As of June 2018, the FBI had removed from its website the reference to the total estimated number of gang members in the United States. In the United States, MS-13 gang members have been involved in local crimes including extortion, drug distribution, prostitution, robbery, and murder, as well as in more transnational illicit activity such as drug trafficking and human smuggling and trafficking. While some of the illegal activities help support the gang's criminal finances, others facilitate the maintenance of territory as well as gang brand and unity. MS-13 has a reputation for particularly violent criminal activity. Some experts see this violence as serving both internal and external purposes. Internally, violence may help recruit—it serves a brand-identifying purpose—in addition to providing discipline and cohesion. Externally, it can help establish territory as well as social and political control. In recent years, this violence has been demonstrated in a reported wave of violent homicides and other criminality attributed to MS-13 in certain locales. For example, authorities have been investigating a spate of killings and other violent activities on Long Island, NY, attributed to MS-13. In May 2017 testimony before the Senate Judiciary Committee, the Suffolk County (NY) police commissioner estimated that since 2016, 38% of murders in the county were attributable to MS-13. In a series of five superseding indictments, federal prosecutors with the Eastern District of New York have indicted two dozen MS-13 members with crimes including at least 15 murders, as well as assaults, arson, and drug distribution. The series of indictments includes charges in the high-profile killings of teenagers Nisa Mickens and Kayla Cuevas. Illustrating a potential increase in MS-13 activity in the Washington, DC, metro area, some suburban jurisdictions have seen an increase in the number of MS-13 members in their county jails. As of February 2018, the Montgomery County, MD, jail reported a 20% increase in the MS-13 population over the previous year. During that same time, the number of MS-13 members in jail increased by 32% in the Prince William County, VA, jail and doubled in the Fairfax County, VA, jail. Countering gang crime is generally the purview of state and local law enforcement. However, given that gang activity is not constrained by jurisdictional boundaries, and that local law enforcement agencies may not have the capacity to investigate complex gang crimes, federal law enforcement has had a long-standing interest in contending with gangs, including MS-13. There is no single federal agency charged with investigating crimes committed by gangs, and federal resources for confronting this threat are allocated across several departments and agencies including the FBI, Drug Enforcement Administration (DEA), Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), and U.S. Immigration and Customs Enforcement (ICE), among others. As the FBI and ICE are often seen as having leading roles in federal gang enforcement efforts, this section largely focuses on their activities. Within the Department of Justice (DOJ), the FBI is charged with investigating violent gangs and runs a number of anti-gang initiatives. One of the primary tools the FBI uses to counter the gang threat is Violent Gang Safe Streets Task Forces, which focus on countering violent gangs and violent crimes. The FBI established the Safe Streets Violent Crime Initiative in 1992 and, through this program, administers Violent Gang Safe Streets Task Forces across the United States. These gang task forces include federal, state, and local law enforcement officers that investigate crimes ranging from racketeering to drug conspiracy and firearms violations. In addition to domestic law enforcement initiatives to counter violent gangs such as MS-13, the FBI has transnational policing partnerships. In 2004, the FBI launched an MS-13 National Gang Task Force (NGTF) to coordinate federal, state, and local investigations of MS-13. This has since evolved into the Transnational Anti-Gang Task Force (TAG) initiative that targets transnational gang threats—with a current focus on MS-13 and the 18 th Street gang. The FBI has established TAG task forces, comprised of FBI agents and vetted local officers, in El Salvador, Guatemala, and Honduras. In addition to being operational task forces, these TAGs facilitate intelligence and information sharing. The TAG initiative also includes the Central American Law Enforcement Exchange (CALEE) program, which helps train local law enforcement in the United States and Central America on gang-related issues and techniques for countering the gang threats. Work of the TAG units can be seen in a number of investigations. For example, in September 2017, through Operation Regional Shield, over 3,800 gang members—from MS-13 and the 18 th Street gang—in the United States, El Salvador, Guatemala, and Honduras were charged with crimes including murder, arson, racketeering, and conspiracy to distribute marijuana; the FBI's TAG units were involved with the investigations in Central America.