The United States and its allies began bombing ISIS targets in Syria using fighters, bomber and Tomahawk missiles, according to the Pentagon late on Monday night.
Here is a look at the rise of the violent group since its inception:
2000: In the early 2000s, Jordanian militant Abu Musab al-Zarqawi sets up the extremist group Tawhid wa al-Jihad (Unity and Jihad)
2003-04: The US and its allies invade Iraq, toppling the regime of Saddam Hussein. Al-Zarqawi forms a splinter group and al Qaeda in Iraq (AQI) opposing Western forces
2006-07: Al-Zarqawi is killed in a US strike. Al-Zarqawi’s successor, Abu Ayyub al-Masri, announces the creation of the Islamic State in Iraq (ISI). The network is weakened in 2007 following the US troop ‘surge’ and the payment of Sunni tribes to form militias to expel AQI
2011-13: The anti-government uprising in neighbouring Syria turns violent and leads to civil war. ISI — now led by Abu Bakr al-Baghdadi — supports Syria’s opposition by setting up the Nusra Front and sending cash and fighters. The group’s brutal tactics are condemned by rebels. Al Qaeda too disowns it. In April, 2013, ISI rebrands itself as ISIS (the Islamic State in Iraq and the Levant). Meanwhile, US troops withdraw from Iraq. Violence perpetrated by ISIS rises
January, 2014: ISIS makes crucial gains in western Iraq and advances to north and east
June 10: Hundreds of jihadists, led by fighters from the ISIS, seize Iraq’s second biggest city Mosul and swathes of Nineveh province. They also overrun parts of the nearby Kirkuk and Salaheddin provinces
June 11: ISIS seizes Tikrit. Storms the Turkish consulate in Mosul, kidnaps the head of the mission and 48 others
June 12: Kurdish forces take over Kirkuk to protect the oil hub from jihadists. Iraqi Kurds want to make Kirkuk part of their autonomous region
June 14: Shiite Iran mulls working with US, its long-time foe.
June 15: Kurdish forces control the Rabia border crossing with Syria
June 16: Militants and security forces battle for Tal Afar. Obama says 275 troops are going to help protect the embassy in Baghdad, their first deployment since US forces withdrew from Iraq
June 17: Militants attack the Baquba, bodies of 18 soldiers and police are found near Samarra
June 18: Militants attack the country’s biggest oil refinery at Baiji, sparking clashes that left dozens dead
June 18: Iraq asks the US to conduct air strikes against jihadist-led Sunni militants, who have seized key cities and large swathes of the country
June 18: Iraq horror hits home, 40 Indian construction workers abducted from Mosul. Ministry of external affairs sets up a crisis management team
June 30: ISIS says it is establishing a caliphate, also proclaims the group’s leader, Abu Bakr al-Baghdadi, as the caliph
July 3: All 46 Indian nurses forcibly moved out by insurgents. They are unharmed, government assures
August 8: President Barack Obama authorises "targeted airstrikes" if needed to protect US personnel from fighters with ISIS
Aug 19: In a video posted on YouTube, US journalist James Foley, missing in Syria since 2012, is decapitated by ISIS militants
Aug 24: ISIS militants storm an air base in northeast Syria, capturing it from government forces after days of fighting that cost more than 500 lives
Aug 28: ISIS fighters execute 250 Syrian soldiers captured when the group seized an air base in the province of Raqqa
Sep 2: ISIS releases a video showing the beheading of another US journalist Steven Sotloff
Sep 8: The Arab League agrees to combat extremists like the ISIS as one of its suicide bombers killed 16 people at a meeting of Sunni tribal fighters and security troops in Iraq
Sep 10: Obama approves US airstrikes in Syria, vows to target and degrade ISIS ‘wherever they exist’
Sep 13: ISIS posts a video showing the execution of British aid worker David Haines, the third beheading of a western hostage in less than a month
Sep 15: World powers back military measures to help defeat ISIS fighters in Iraq, boosting Washington’s efforts to set up a coalition, but make no mention of the tougher diplomatic challenge next door in Syria
Sep 17: ISIS releases video warning the US that its fighters are waiting for it in Iraq if Obama sends troops there, as his top general said may happen if the current strategy of airstrikes fails
Sep 17: Obama meets commanders to decide on plan to target ISIS as Iraqi army launches offensive
Sep 19: ISIS releases another video showing British journalist, who says he is being held hostage by the extremists.
Sep 20: Forty-nine Turks held hostage for months by Islamic State jihadists in northern Iraq were freed and returned to Turkey
Sep 22: US launches airstrikes on ISIS targets in Syria
Sep 8: The Arab League agrees to combat extremists like the ISIS as one of its suicide bombers killed 16 people at a meeting of Sunni tribal fighters and security troops in Iraq
Sep 10: Obama approves US airstrikes in Syria, vows to target and degrade ISIS ‘wherever they exist’
Sep 13: ISIS posts a video showing the execution of British aid worker David Haines, the third beheading of a western hostage in less than a month
Sep 15: World powers back military measures to help defeat ISIS fighters in Iraq, boosting Washington’s efforts to set up a coalition, but make no mention of the tougher diplomatic challenge next door in Syria
Sep 17: ISIS releases video warning the US that its fighters are waiting for it in Iraq if Obama sends troops there, as his top general said may happen if the current strategy of airstrikes fails
Sep 17: Obama meets commanders to decide on plan to target ISIS as Iraqi army launches offensive
Sep 19: ISIS releases another video showing British journalist, who says he is being held hostage by the extremists.
Sep 20: Forty-nine Turks held hostage for months by Islamic State jihadists in northern Iraq were freed and returned to Turkey
Sep 22: US launches airstrikes on ISIS targets in Syria