A Free Syrian Army fighter runs after attacking a tank with a rocket-propelled grenade during fighting in Aleppo, Syria, in September 2012. The rebels say they are willing to take on the Islamic State, but need more weapons. Manu Brabo/AP hide caption

itoggle caption Manu Brabo/AP

Saudi Arabia's oil minister, Ali Al-Naimi, shown in Kuwait last month, has played down the drop in oil prices. The country continues to pump oil at high levels, saying it wants to preserve its market share. But this has also contributed to a 25 percent drop in oil prices since June. Yasser Al-Zayyat/AFP/Getty Images hide caption

itoggle caption Yasser Al-Zayyat/AFP/Getty Images

Thick smoke rises following an airstrike by the U.S.-led coalition in Kobani, Syria, while fighting continued between Syrian Kurds and the militants of the self-proclaimed Islamic State, as seen from Mursitpinar on the outskirts of Suruc, at the Turkey-Syria border on Wednesday. Lefteris Pitarakis/AP hide caption

itoggle caption Lefteris Pitarakis/AP

Abdul-Rahman Kassig, who was formerly known as Peter, is shown with a truck filled with aid supplies for Syrian refugees. The American aid worker was seized by the Islamic State in October 2013 and the group is now threatening to kill him. Courtesy of Kassig Family hide caption

itoggle caption Courtesy of Kassig Family

Smoke rises after a U.S.-led coalition airstrike on Kobani, Syria, Monday, as seen from the Turkish side of the border. Kurdish fighters say they're making progress against ISIS in the area. Tolga Bozoglu/EPA/LANDOV hide caption

itoggle caption Tolga Bozoglu/EPA/LANDOV

Iranian women look at the palace of King Darius of Achaemenid Persepolis, near Shiraz in southern Iran. Behrouz Mehri/AFP/Getty Images hide caption

itoggle caption Behrouz Mehri/AFP/Getty Images