July 2014 - In Syria, all the cities between Deir Ezzor city and the Iraq border have fallen to ISIS, says Omar Abu Leila, a spokesman for the rebel Free Syrian Army.
July 3, 2014 - ISIS takes control of a major Syrian oil field, al-Omar. It is the country's largest oil field and can produce 75,000 barrels of oil daily.
July 17, 2014 - In Syria's Homs province, ISIS claims to have killed 270 people after storming and seizing the Shaer gas field.
July 24, 2014 - ISIS militants blow up Jonah's tomb, a holy site in Mosul.
August 8, 2014 - Two U.S. F/A-18 jet fighters bomb artillery of Sunni Islamic extremists in Iraq. President Barack Obama has authorized "targeted airstrikes" if needed to protect U.S. personnel from fighters with ISIS. The U.S. military also could use airstrikes to prevent what officials warn could be a genocide of minority groups by the ISIS fighters.
August 19, 2014 - In a video posted on YouTube, U.S. journalist James Foley, missing in Syria since 2012, is decapitated by ISIS militants. The militants then threaten the life of another captured U.S. journalist, believed to be Steven Sotloff.
September 2, 2014 - ISIS releases a video showing the beheading of U.S. journalist Steven Sotloff. Sotloff's apparent executioner speaks in what sounds like the same British accent as the man who purportedly killed Foley. He's dressed identically in both videos, head to toe in black, with a face mask and combat boots. He appears to be of similar build and height. He waves a knife in his left hand, as did the militant in the video of Foley's death.
September 11, 2014 - The CIA announces that the number of people fighting for ISIS may be more than three times the previous estimates. Analysts and U.S. officials initially estimated there were as many as 10,000 fighters, but now ISIS can "muster between 20,000 and 31,500 fighters across Iraq and Syria," a CIA spokesman tells CNN.
September 13, 2014 - ISIS militants post video on a website associated with the group, showing the apparent execution of British aid worker David Haines. This makes him the third Western captive to be killed by the Islamist extremist group in recent weeks. ISIS directs a statement at British Prime Minister David Cameron, threatening more destruction if Britian continues its "evil alliance with America." At the end of the video, the executioner threatens the life of Alan Henning, another British citizen held captive. The executioner appears to be the same one who killed both Steven Sotloff and James Foley.
September 23, 2014 - The United States carries out airstrikes against ISIS. The bombing is focused on the ISIS stronghold of Raqqa, a city in northern Syria.