From the Doucment: "Al Shabaab (aka 'Harakat Al Shabaab Al Mujahidin,' or Mujahidin Youth Movement) is an insurgent and terrorist group that emerged in the mid-2000s amid a vacuum of state authority in Somalia. The group evolved out of a militant wing of the Union of Islamic Courts (UIC), which took control of Somalia's capital, Mogadishu, in 2006. Neighboring Ethiopia, which backed Somalia's nascent transitional government, intervened militarily to oust the UIC. Al Shabaab used historical anti-Ethiopian sentiment among Somalis to attract recruits and support, including among the diaspora in the United States. Al Shabaab held much of south-central Somalia, including Mogadishu, from the late 2000s until the U.N.-authorized African Union (AU) Mission in Somalia (AMISOM) gained momentum against the insurgency in 2011-2012. Despite its territorial losses and the formation of a new federal government in Mogadishu in 2012, Al Shabaab has retained control or influence over large areas of the country."
CRS In Focus, IF10170
Congressional Research Service: https://crsreports.congress.gov/