For years before Saturday's unsuccessful raid in Somalia to capture a top al Shabaab militant, Washington had waged a secret law enforcement and spy war against the group, which claimed responsibility for last month's deadly assault on a Kenyan shopping mall but has little record of targeting the United States.
A low-profile New York federal court case offers a rare glimpse into that clandestine offensive, which involves not only U.S. military special forces assaults like the one early on Saturday on the Somali port town of Barawe, but drone strikes and a controversial counter-terrorism tactic known as rendition.
In a secret operation late last summer, U.S. authorities questioned three former European al Shabaab militants in an African jail, took custody of them with few judicial formalities, flew them to New York and filed terrorism charges against them.
Ali Yasin Ahmed and Mohamed Yusuf, both Swedish citizens, and Mahdi Hashi, a former British citizen, were charged in federal court in Brooklyn with conspiring to provide material support to a foreign terrorist group, providing such support, and violating U.S. firearms laws. They entered not guilty pleas.
The case has an unusual twist: U.S. prosecutors do not allege the suspects posed a specific threat to the United States.
This strategy appears to raise questions about how broadly the U.S. interprets its counter-terrorism laws, and whether others will view it as trying to be a global policeman against terrorism.
Al Shabaab, which seeks to impose conservative Islamic rule in Somalia, has factions allied with the global al Qaeda movement, but has largely focused its activities in East Africa. It has attacked Washington's regional allies, rather than directly striking U.S. targets.
U.S. Navy SEALS stormed ashore into the al Shabaab stronghold of Barawe on Saturday in response to the September attack on the Westgate mall in Kenya but, a U.S. official said, they failed to capture or kill their unnamed target.
A SEAL raid in the same area four years earlier killed another top al Shabaab leader, Saleh Ali Saleh Nabhan.
In announcing the trio's arrests in the Brooklyn case, U.S. Attorney Loretta Lynch said, "We will use every tool at our disposal to combat terrorist groups, deter terrorist activity, and incapacitate individual terrorists."
Officials and defense lawyers said U.S. courts have in the past upheld similar charges against militants arrested overseas under U.S. counter-terrorism laws for crimes outside the United States.
But Harry Batchelder, a defense lawyer who until recently represented Hashi, questioned how U.S. law was applied in the New York cases.
"If we carried this to its logical conclusion, we'd have to build a (new prison) wing to (house) al Shabaab," he said.
While some aspects of the New York case have been previously reported, Reuters has learned new details, particularly about Hashi's alleged activities.
British activist groups sympathetic to Hashi report that he has recently started a hunger strike. Neither his current lawyer nor a spokesman for the U.S. Attorney's office in Brooklyn could be reached for comment.
The FBI said in a statement that between late 2008 and the summer of 2012, the three defendants "participated in weapons and explosives training with members and associates" of al Shabaab and "were also deployed in combat operations to support Shabaab's military activities in Somalia."
Investigators and legal sources also say that Yusuf, using the name Abu Zaid, made a video in 2010 in which he threatened to behead a Danish cartoonist who had lampooned the Prophet Mohammad.
However, sources close to the men's defense teams who have talked to the suspects and their associates say that when they were detained in August 2012 in Djibouti, they were trying to flee Somalia and leave al Shabaab. They were en route to Yemen, perhaps to make their way back to Europe.
Legal sources familiar with the case described it as one of the more notable uses under U.S. President Barack Obama of "rendition," in which a suspect is captured and moved between countries without the formal legal proceedings which normally accompany an extradition.
In the aftermath of the Sept. 11, 2001, attacks, the CIA carried out a series of "extraordinary renditions," capturing suspected militants in countries such as Pakistan and Afghanistan and transferring them without judicial review to secret prisons run by the spy agency, or to third countries.
Obama has not renounced the practice, and U.S. military forces on Saturday staged a second raid, in Libya, capturing Abu Anas al-Liby, whom the United States has indicted for his alleged role in the 1998 bombings of U.S. embassies in Kenya and Tanzania.
After being held for a time in a Djibouti prison - where the former al Shabaab militants allege they were treated roughly by local authorities - they were questioned by a team of U.S. investigators, who said little about their objectives or identities. Then they were questioned by a second U.S. team who identified themselves as FBI investigators.
Then, with little or no judicial review in Djibouti, the men were flown to New York. After first being detained in secret, they were charged in November and ordered held without bail.
A main objective of the U.S. operation appears to have been to collect intelligence about al Shabaab.
Information on the group has become more urgent for security services following the deadly attack by militants on the upscale Westgate shopping mall in Nairobi. At least 67 people were killed in a four-day siege.
Ahmed Godane, the leader of Shabaab's dominant, pro-al Qaeda faction, claimed credit for the attack.
Defense lawyers said that once Ahmed, Yusuf and Hashi, all of Somali extraction, were in the United States, investigators began pressuring them to provide information about al Shabaab's leaders and operations.
"It's all about getting information," said Susan Kellman, a lawyer for Ahmed.
But the three have not agreed to cooperate, legal sources familiar with the case said. The suspects intend to challenge their indictments in court, though a trial date has not been set.
In a possible ploy to increase pressure on the defendants, federal prosecutors last month placed a letter in the public court record alleging the former fighters had "substantial knowledge" of a purported Shabaab "research and development department" involved in developing chemical weapons.
Defense lawyers and even some U.S. and European security sources question the timing of the U.S. government's claim, which came after international uproar over a gas attack in Syria. They said there is little evidence pointing to Shabaab's involvement in chemical weapons.
Hashi, the former London resident, traveled a perilous course in which apparently he ran afoul of both al Shabaab and Western intelligence.
In 2010, British authorities revoked Hashi's British citizenship, meaning that when he was later picked up by the Americans, he could make no appeal to London for help.
Sources familiar with the case said the British took this action because they had insufficient evidence to prosecute Hashi for terrorism-related offenses under British law, but did not want him to return to Britain.
During sojourns with al Shabaab in Somalia, Hashi acted as an associate, or lieutenant, to a high-ranking leader of the group named Bilal Al-Berjawi, those familiar with his case said.
Berjawi was reportedly wounded in a 2011 air strike on an al Shabaab base. That same year, British authorities revoked his British citizenship. British officials declined to comment on the case.
In January 2012, Berjawi was reported killed in a U.S. drone strike.
Al Shabaab leaders grabbed Hashi, imprisoned him, and beat him up, possibly because they suspected he had some role in Berjawi's death, said a source familiar with the case. But eventually al Shabaab "cleared" Hashi and he left the group with the two Swedes, the source said.
Both U.S. officials and defense sources confirm that the men were in transit to Yemen when they were detained. But defense lawyers dispute investigators' assertions that the suspects intended to join Yemen-based al Qaeda in the Arabian Peninsula, widely regarded as central al Qaeda's most deadly spinoff.
Not long after the men headed for Yemen, al Shabaab said on its Twitter feed that it had executed three other men for spying for the CIA and MI5 and helping them kill Berjawi.
Hashi's two co-defendants, Ahmed and Yusuf, remain citizens of Sweden. Gabriella Augustsson, a spokeswoman for Sweden's embassy in Washington, said that a Swedish consular official had visited the two and been in contact with their lawyers.