Oct. 17, 2017: US-backed forces fighting ISIS in Raqqa say "major military operations" in the city have ended and that the jihadists have lost control of their self-declared capital. The development marks a decisive victory in the fight against ISIS, though US officials said there were still pockets of resistance in the city.
July 2017: Iraqi PM and commander of the armed forces, Haider al-Abadi, declares that Mosul city is completely liberated from ISIS.
Only a "couple of hundred" ISIS fighters remain in Mosul, as a US-led coalition continues to rid the terror group from Iraq's second-largest city, a coalition spokesman said in June 2017.
While its exact size is unclear, the group is thought to include thousands of fighters.
ISIS has been led by a man named Abu Bakr al Baghdadi since 2010. Not much is known about him, but a biography posted on jihadist websites last year said he held a Ph.D. in Islamic studies from a university in the capital. He also served four years in a U.S. prison camp for insurgents in southern Iraq.
The group has exploited a growing perception among many Sunni Muslims that they are being persecuted by the Shia-dominated government led by Iraqi Prime Minister Nuri al-Maliki, starved of resources and excluded from a share of power.
It wants to establish an Islamic caliphate, or state, stretching across the region ruled by Sharia law.
ISIS is highly fanatical, killing Shia Muslims and Christians whenever possible, as well as militarily efficient and under tight direction by top leaders. Here, they are purported to be shown executing Iraqi security forces.
On Nov. 6, 2015, President Barack Obama addresses the nation and vows to destroy ISIS in a relentless, strong and smart campaign that is consistent with the nation's values.
ISIS seized Mosul, Iraq's second-largest city, in early June 2014 and has threatened to march into Baghdad. The northwest Iraqi city of Tal Afar has also fallen to ISIS, as have two villages northeast of Baghdad.
The group subsequently beheaded two American journalists, claiming their deaths were in retaliation for U.S. airstrikes targeting ISIS. A video was released showing James Foley's (right) death on Aug. 19, 2014, and a video showing the death of Steven Sotloff (right) was released Sept. 2, 2014.
In February of 2015, Egypt launched airstrikes aimed at ISIS-affiliated jihadists in Libya who are believed to have killed 21 Egyptian Coptic Christians, including about a dozen whose beheadings are featured in a video published by the organization.
In May 2015, ISIS forces extended their control around the ancient Syrian city of Palmyra. The capture of Syria's ancient city, about 150 miles northeast of Damascus, threatens a UNESCO World Heritage Site described as having "stood at the crossroads of several civilizations,"
Over 350 people were hurt in a coordinated attack by three teams at locations in Paris in November of 2015. ISIS claimed responsibility for the attack.
Iraqi troops managed to wrest control of Ramadi from ISIS in February of 2016.