(CBS News) WASHINGTON - Most Americans had heard little - or nothing - about al-Shabab, the Somali terror group that, before this weekend.
Since 2006, al-Shabab has been trying to establish strict Islamic law inside Somalia, taking advantage of a dysfunctional government.
The group, affiliated with al Qaeda, has carried out a series of bombings in Somalia's capital, Mogadishu. Two weeks ago, 15 people were killed when a car bomb and a suicide bomber attacked a restaurant.
Recently, al-Shabab has been under pressure from government forces and has abandoned some bases in southern Somalia.
But al-Shabab is fighting to re-establish its brand and extend its reach.
In 2010, al-Shabab militias went beyond Somalia's borders to carry out twin bombings in Uganda that.
Now comes the attack in Kenya. Al-Shabab says it's in retaliation for Kenyan troops participating in the fight against al-Shabab in Somalia.
But the massacre is also a propaganda tool to convince extremists the group is still relevant.
Historically, al-Shabab has been al Qaeda's most effective recruiter of American jihadists.
Using Internet videos with English-speaking operatives, the terror group has.
"You are the one in need, you know?" one operative said in a video. "You are the one in need, and we are all in need of Allah."
Intelligence sources say at least 15 of the American recruits have already died in various terror operations, including suicide bombings.
The Americans are also caught in a power struggle inside al-Shabab. One of the leading propagandists, Alabama-born Omar Hammami, publicly broke with the group. Sources say he.
Sources tell us the flow of Americans to Somalia has greatly slowed, but it has not stopped.