Read the full comprehensive report, Al Shabaab's American Recruits (PDF).
A wave of Americans traveling to Somalia to fight with Al Shabaab, an Al Qaeda-linked terrorist group, has been described by the FBI as one of the "highest priorities in anti-terrorism."
Americans began traveling to Somalia to join Al Shabaab in 2007, around the time the group stepped up its insurgency against Somalia's transitional government and its Ethiopian supporters, who have since withdrawn.
These Americans have received weapons training alongside recruits from other countries, including Britain, Australia, Sweden and Canada, and have used the training to fight against Ethiopian forces, African Union troops and the internationally-supported Transitional Federal Government in Somalia, according to court documents.
Most of the American men training with Al Shabaab are believed to have been radicalized in the U.S., especially in Minneapolis, according to U.S. officials. The FBI alleges that these young men have been recruited by Al Shabaab both on the Internet and in person.
One such recruit from Minneapolis, 22-year-old Abidsalan Hussein Ali, was one of two suicide bombers who attacked African Union troops on October 29, 2011. He was identified by his family as speaking in an audio message released by Al Shabaab claiming credit for the bombing. Somali authorities reported that 10 people were killed in the ensuing firefight.
Ali is the third American suicide bomber. The first, Shirwa Ahmed, carried out a suicide bombing at the Ethiopian Consulate and the presidential palace in Hargeisa killing 24 people in October 2009. The second, Farah Mohamad Beledi, carried out a suicide bombing on May 30, 2011, targeting a military base outside Mogadishu, the Somali capital, killing two African Union peacekeepers and a Somali soldier. Federal investigators have also looked into reports about whether another American was involved in a suicide attack in Mogadishu in September 2009 that killed 21 people. The identity of that attacker has never been confirmed.
Additionally, Al Shabaab claimed that three Americans took part in its assault on the Westgate Mall in Nairobi, Kenya, on September 21, 2013. Al Shabaab named Ahmed Mohamed Isse of St. Paul, Minnesota, Abdifatah Osman Keenadiid of Minneapolis, and Gen Mustafe Noorudiin of Kansas City, Missouri as attackers via the organization’s Twitter feed. As of October, 2013, Al Shabaab’s claims had not been verified by American law enforcement. In addition, other Twitter accounts claiming to be Al Shabaab have suggested that other Americans were also involved.
FBI director Robert Mueller said he was "absolutely" concerned that the young American men may return to the U.S. with their passports and attempt to carry out an attack on U.S. soil similar to the foiled plot in Australia, in which Somali-Australians allegedly affiliated with Al Shabaab planned to carry out a suicide attack on a Sydney army base after returning from Somalia.
While there have been no similar plots in the United States to date, Al Shabaab's desire to expand its operations outside of Somali and its ability to attract American recruits, presents a significant threat to the U.S.
A version of this report was first published in February, 2012.