A Somali police officer arrests a suspected rebel member of the al Qaeda-affiliated al Shabaab among beach goers in Mogadishu. Al Shabaab claimed responsibility for today's pre-dawn attack on a Kenyan university campus near the Somali border. The following gallery examines who is al Shabaab. Here: Somali police officer (R) arrests a suspected rebel member (L) of the Al Qaeda-affiliated al Shabaab among beach goers at the Lido beach north of Somalia's capital Mogadishu March 23, 2012. (Photo by Feisal Omar/Reuters)

Factory landlord Lawrence Taylor (L), portraying a Colour Sergeant from the King's Royal Rifle Corps, part of the Rifles Living History Society, performs a drill with Connor Young (R) of the Queen's Own Royal West Kent Regiment Living History Group as they recreate the life of a First World War soldier at the Eden Valley Museum in Edenbridge in southeast England May 10, 2014. Lawrence has always had an interest in military history and specifically “The Rifles” – his veteran father's WWII regiment. When he became a re-enactor he chose not to re-enact WWII as many of the veterans are still alive, and he felt uncomfortable as he remembers his father would have flashbacks and nightmares about the war. United by a fascination with military history and a fondness for dressing up, groups such as the Rifles Living History Society and the Queen's Own Royal West Kent Regiment Living History Group get together to recreate aspects of life during the First World War. Reuters photographer Luke MacGregor photographed members of the groups, both as they took part in living history events and at their day jobs. (Photo by Luke MacGregor/Reuters)

Liu Chunxia, a supporter of Xu Zhiyong, one of China's most prominent rights advocates, is detained by policemen while she gathers with other supporters nearby a court where Xu's trial is being held in Beijing January 22, 2014. When dozens of activists unfurled banners across the country last March and April calling for officials to disclose their assets, they did so at the urging of one of China's most prominent rights advocates, Xu Zhiyong. Xu, 40, stands trial on Wednesday on a charge of “gathering a crowd to disturb public order” punishable by up to five years in prison. His case will almost certainly spark fresh criticism from Western governments over Beijing's crackdown on dissent. (Photo by Kim Kyung-Hoon/Reuters)

A visitor holds an Israeli-made rifle during the 8th International Land and Naval Defense system exhibition, in New Delhi, India, on February 6, 2014. (Photo by Anindito Mukherjee/Reuters)

Daniel Ricciardo performs alongside Michael Kneightley in an RAAF F/A-18 Hornet at RAAF Base in East Sale, Victoria, Australia on March 12th, 2014. (Photo by Andy Green/Red Bull Content Pool)

Elephants spray tourists with water in celebration of the Songkran water festival in Thailand's Ayutthaya province, about 80 km (50 miles) north of Bangkok, April 9, 2014. (Photo by Rungroj Yongrit/EFE)

Passengers from the ferry sinking off South Korea's southern coast are rescued by the South Korean Coast guard in the water off the southern coast near Jindo, south of Seoul, on April 16, 2014. Almost 300 people were missing after a ferry sank off South Korea on Wednesday, the coastguard said, in what could be the country's biggest peacetime disaster in nearly 20 years. (Photo by AP Photo)

Beachgoers watch the detonation of a 500 pound British bomb on the beach on May 19, 2014 in Wassenaar, Netherlands. The bomb was dropped by the British allied forces during the second world war over nearby Leiden where it was found on a building site. (Photo by Michel Porro/Getty Images)