Islamic State, also known as ISIS or ISIL, controls the cities of Mosul in Iraq and Raqqa in Syria and is proving a potent threat abroad, claiming credit for major attacks in Paris in November and Brussels in March.
But there are mounting indications that the momentum in Iraq and Syria has shifted against Islamic State.
U.S. officials say the group is losing a battle to forces arrayed against it from many sides in the vast region it controls. In Iraq, the group has been pulling back since December when it lost Ramadi, the capital of the western province of Anbar. In Syria, the jihadist fighters have been pushed out of the strategic city of Palmyra by Russian-backed Syrian government forces.
- Syrian forces seek to extend gains after re-taking Palmyra from ISIS
- Trapped civilians in Anbar slow Iraqi advance against ISIS
- Iraqi mud and political quagmire bog down battle for ISIS-held Mosul
- Fighting over ISIS-held Mosul displaces hundreds of Iraqis
Since U.S.-backed forces recaptured the strategic Syrian town of al-Shadadi in late February, a growing number of Arab fighters in Syria have offered to join the fight against the group, the U.S. officials said.
U.S. forces have also had increased success in eliminating top ISIS leaders. Air strikes in recent weeks killed a top official called Abd al-Rahman Mustafa al-Qaduli, and an Islamic State commander described as the group's "minister of war" -- Abu Omar al-Shishani, or Omar the Chechen.
The United States announced last December it was deploying a new force of special operations troops to Iraq to conduct raids against Islamic State there and in neighboring Syria. That followed its announcement in October that dozens of U.S. special forces would be deployed in Syria, the first U.S. ground troops to be stationed there.