The U.S. recently revealed that it had captured an al Shabaab leader, Ahmed Abdulkadir Warsame, two years ago. Details of this had been kept secret because Warsame agreed to provide a lot of information about al Shabaab and al Qaeda in return for a lighter sentence. Warsame was captured at sea as he was travelling by boat from Yemen to Somalia. He admitted he had worked as an Islamic terrorist and taught bomb making and other terrorism techniques. In Somalia Warsame commanded several hundred al Shabaab fighters and also arranged arms shipments from al Qaeda stocks in Yemen.
Warsame’s capture was no secret, but his cooperation was, until now. Apparently that cooperation continues and no details of exactly what information Warsame provided have been made public. Keeping Warsame’s cooperation quiet was necessary so as not to give warning to his terrorist associates that he was giving them up. It also made it possible to safeguard kin of Warsame, who might be subject to terrorist reprisal if his cooperation were revealed too soon. That might have happened because Warsame was a bright guy who had risen fast in al Qaeda and had direct contact with many senior al Qaeda officials.
Warsame knew a lot and he talked. That is rare with Islamic terrorist leaders, especially very well connected ones.