Yemeni soldiers hold up their weapons at an area seized from al-Qaida in the southeastern province of Shabwa, Yemen, on May 8. President Obama said Wednesday that U.S. strategy against the so-called Islamic State would be similar to how it targeted militants in Yemen and Somalia. Yemen's Defense Ministry/AP hide caption

itoggle caption Yemen's Defense Ministry/AP

A money changer sits behind piles of banknotes in Hargeisa in Somaliland, an autonomous, relatively peaceful region in northern Somalia. The self-declared nation of Somaliland, like Somalia itself, lacks a formal banking system, and residents rely on hawaladars to receive money from abroad. Simon Maina/AFP/Getty Images hide caption

itoggle caption Simon Maina/AFP/Getty Images

Chief Warrant Officer Michael Durant, wounded when the helicopter he was piloting was shot down in Somalia, arrives at Andrews Air Force Base in Maryland, on Oct. 16, 1993. He was held captive for 11 days. Joe Marquette/AP hide caption

itoggle caption Joe Marquette/AP

Heavy smoke rises from the Westgate Mall in Nairobi, Kenya, on Monday. The Somali militant group al-Shabab claimed responsibility for the attack. Jerome Delay/AP hide caption

itoggle caption Jerome Delay/AP

Somali women and children wait to get medicine in July 2008, from a clinic run by Doctors Without Borders about 20 miles south of Mogadishu. AFP/AFP/Getty Images hide caption

itoggle caption AFP/AFP/Getty Images

Ali Maow Maalin said he avoided getting the smallpox vaccine as a young man because he was afraid of needles. He didn't want others to make the same mistake with polio. Courtesy of the World Health Organization hide caption

itoggle caption Courtesy of the World Health Organization

A Yemeni child receives a polio vaccine in the capital city of Sanaa. The Yemen government launched an immunization campaign last month in response to the polio outbreak in neighboring Somalia. Mohammed Huwais/AFP/Getty Images hide caption

itoggle caption Mohammed Huwais/AFP/Getty Images