Iraq's Prime Minister Haider al-Abadi, speaking Thursday in Washington, said recent battlefield victories showed the Islamic State could be defeated. The extremist group still holds large parts of the west and the north of Iraq. Kevin Wolf/Kevin Wolf hide caption

itoggle caption Kevin Wolf/Kevin Wolf

American journalist Ned Parker (foreground) is the Reuters bureau chief in Baghdad. He fled Iraq last week after receiving threats in response to reports on human rights abuses by Shiite militias allied with Iraq's government. He's shown here at Iraq's Foreign Ministry in 2007. Courtesy of Ned Parker hide caption

itoggle caption Courtesy of Ned Parker

Iraqi Prime Minister Haider al-Abadi and President Obama meet at the White House on Tuesday. The prime minister is visiting to discuss the fight against the self-proclaimed Islamic State. Jacquelyn Martin/AP hide caption

itoggle caption Jacquelyn Martin/AP

Former Blackwater security guards were sentenced Monday for the shooting of dozens of Iraqi civilians in Nisour Square in Baghdad, Iraq. The square is seen here on Sept. 20, 2007, four days after the incident. Khalid Mohammed/AP hide caption

itoggle caption Khalid Mohammed/AP

Members of the Shiite militia group Kataib Hezbollah train at a military base near Samarra, in northern Iraq, on March 5. The Shiite militia stands accused of retaliatory violence against Sunnis in an area it helped retake from ISIS. Baraa Kanaan/EPA/Landov hide caption

itoggle caption Baraa Kanaan/EPA/Landov

Iraqi security forces, most of them Shiite Muslims, gather Thursday in Tikrit at the entrance of a palace that belonged to the former dictator Saddam Hussein. The Islamic State, a Sunni extremist group, had held Tikrit since last summer. When it was in control, the group painted its black flag on a blast wall at the entrance to the compound. Khalid Mohammed/AP hide caption

itoggle caption Khalid Mohammed/AP

Iraqi security forces and allied Shiite militiamen look for Islamic State extremists in Tikrit on Tuesday. Iraqi forces were going house-to-house in search of snipers and booby traps. Khalid Mohammed/AP hide caption

itoggle caption Khalid Mohammed/AP