The US military expanded its war against the Islamic State in Iraq and Syria (ISIS) on Sept 22, 2014 by sending waves of warplanes and launching Tomahawk cruise missiles into Syria to attack an array of targets in an aggressive and risk-laden operation that marks a new phase in the conflict.
Here is a quick look at the extremist group and how the conflict has developed so far.
1. The organisation was originally led by Abu Musab al-Zarqawi, a Jordanian and a convicted thief before he turned to radical Islam and formed his group of fighters drawn from Iraq and a region known in Arabic as the "al-Sham" or the Levant, that is Palestine, Lebanon and Syria.
2. In 2004, the group, then known as the Al Qaeda in Iraq, pledged allegiance to Al Qaeda. But differences persisted between Zarqawi and Osama bin Laden's key adviser Ayman al-Zawahiri. Zarqawi's campaign was known for its savagery and targeting of Shi'ites in Iraq. Zawahiri counselled against beheadings and killing of Shi'ites.
Syrian Kurds, fleeing Islamic State militants, walk after crossing into Turkey at the Turkish-Syrian border, near the southeastern town of Suruc in Sanliurfa province, Sept 20, 2014. -- PHOTO: REUTERS
3. Zarqawi was killed in 2006. And efforts mounted to rein in his followers. But the outbreak of war in Syria provided fresh opportunity for the group.
4. The group's emir now is Abu Bakr al-Baghdadi, who claims to be a direct descendant of Prophet Mohammed. He took over in 2010 and the group now calls itself the Islamic State in Iraq and al-Sham (ISIS) or the Islamic State (IS).
5. In 2011, it managed to free hundreds of Iraqi prisoners and began a campaign to strengthen itself by inducting several young fighters.
Turkish soldiers stand guard as Syrian Kurds, fleeing an advance by Islamic State militants, wait behind a border fence near the southeastern town of Suruc in Sanliurfa province Sept 22, 2014. -- PHOTO: REUTERS
6. Its goal is still to establish a hardline Sunni Islamic state. Some experts say it could become deadlier than the Al-Qaeda in its present state. ISIS still retains influence over parts of Syria, controlling some of the eastern oilfields. ISIS uses revenue from these oilfields to fund its insurgency operations.
7. In Iraq, the group's major breakthrough was a capture of the city of Mosul in June. Parts of Tikrit, Saddam Hussein's hometown which is 152.8km from Baghdad, are now said to be under its control.
8. Gains by the militants, including the siege of Iraq's biggest oil-refinery at Baiji, despite the presence of thousands of security troops, have led to concerns about future moves by the insurgents and their likely impact on oil prices.
A displaced Iraqi child, who fled from Islamic State violence in Mosul, helps her family to wash dishes at Baherka refugee camp in Erbil Sept 19, 2014. -- PHOTO: REUTERS
2004 - Abu Musab al-Zarqawi establishes Al-Qaeda in Iraq (AQI).
2006 - Under al-Zarqawi, Al-Qaeda in Iraq tries to ignite a sectarian war against the majority Shia community.
June 7, 2006 - Al-Zarqawi is killed in a U.S. strike. Abu Ayyub al-Masri, also known as Abu Hamza al-Muhajer, takes his place as leader of AQI.
October 2006 - AQI leader Abu Ayyub al-Masri announces the creation of Islamic State in Iraq (ISI), and establishes Abu Omar al-Baghdadi as its leader.
April 2010 - Abu Bakr al-Baghdadi becomes leader of ISI after Abu Omar al-Baghdadi and Abu Ayyub al-Masri are killed in a joint U.S.-Iraqi operation.
April 8, 2013 - ISI declares its absorption of an al Qaeda-backed militant group in Syria, Jabhat al-Nusra, also known as the al-Nusra Front. Al-Baghdadi says that his group will now be known as ISIS.
April 2013 - Al-Nusra Front leader Abu Mohammed al-Jawlani rejects ISIS's attempt to merge with the group.
February 3, 2014 - Al Qaeda renounces ties to ISIS after months of infighting between al-Nusra Front and ISIS.
May 2014 - ISIS kidnaps more than 140 Kurdish schoolboys in Syria, forcing them to take lessons in radical Islamic theology.
A man walks at a makeshift oil refinery site in al-Mansoura village in Raqqa's countryside, where Islamic State has its strongholds, in this picture taken on May 5, 2013.
June 9, 2014 - Monday night into Tuesday, militants seize Mosul's airport, its TV stations and the governor's office. ISIS frees up to 1,000 prisoners.
June 10, 2014 - ISIS takes control of Mosul.
June 11, 2014 - ISIS takes control of Tikrit.
June 21, 2014 - ISIS takes control of Al-Qaim, a town on the border with Syria, as well as three other Iraqi towns.
June 28, 2014 - Iraqi Kurdistan restricts border crossings into the region for refugees fleeing the fighting.
June 29, 2014 - ISIS announces the creation of a caliphate (Islamic state) that erases all state borders, making al-Baghdadi the self-declared authority over the world's estimated 1.5 billion Muslims. The group also announces a name change to the Islamic State (IS).
June 30, 2014 - The United Nations announces that an estimated 1.2 million Iraqis have been forced from their homes.
June 30, 2014 - The Pentagon announces the United States is sending an additional 300 troops to Iraq, bringing the total U.S. forces in Iraq to nearly 800. Troops and military advisers sent to Iraq are there to add security to the U.S. Embassy and the airport in Baghdad, and to provide support to Iraqi security forces.
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.
Bullet holes cover a building after heavy fighting between Islamic State group jihadists and Iraqi militia and government security forces in Dhuluiya, some 75 kms (45 miles) north of Baghdad on September 17, 2014. -- PHOTO: AFP
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.
Sept 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.
Sept 10, 2014 - Obama announced expanded air strikes in Iraq, part of a broader strategy to combat Islamic militants in Iraq and Syria. He also offered the first hint that he would be willing to launch similar strikes in Syria, even as he stressed Washington's continued opposition to Syrian leader Bashar al-Assad.
Sept 11, 2014 - The CIA announces that the number ofpeople 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.
Sept 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.
Sept 14, 2014 - British Prime Minister David Cameron said Britain was ready to "take whatever steps are necessary" to destroy the ISIS militants, but he resisted pressure to join the United States in announcing air strikes.
Sept 15, 2014 - The world's top diplomats pledged to support Iraq in its fight against the ISIS by any means necessary, including "appropriate military assistance", as leaders stressed the urgency of the crisis. Representatives from around 30 countries and international organisations, including the United States, Russia and China, gathered in Paris to condemn the beheading of the third Western hostage.
Sept 17, 2014 - Elite Iraqi troops backed by US jets battled ISIS militants near Baghdad, as Washington devised a strategy for expanded operations against the militants.
Sept 18, 2014 - Australia's security forces foiled an alleged plot by ISIS militants to carry out a beheading in Sydney and arrested 15 people in the country's biggest anti-terrorism operation. The pre-dawn raids in Sydney and Brisbane reportedly uncovered machetes, balaclavas, military fatigues and a scimitar, all apparently meant for use in attacks within days. In the United States, lawmakers took their first tentative step towards approving Obama's strategy against the ISIS, with the House backing a controversial plan to arm and train moderate Syrian rebels.
Sept 22, 2014 - Australia announced new anti-terrorism laws, including enhanced powers for security agencies to detain terror suspects and conduct long-term surveillance.
Sept 23, 2014 - The US and its five Middle East allies moved the Obama plan to battle ISIS into a new phase, as waves of drones and bombers, together with a barrage of some 50 Tomahawk missiles, pounded targets in Syria. The US President said the presence of the five partners - Bahrain, Jordan, Saudi Arabia, Qatar and the United Arab Emirates - was a clear demonstration that this was not a US fight alone.
Sept 24, 2014 - The United Nations Security Council unanimously approved a resolution cracking down on the flow of foreign fighters to terrorist groups at a session chaired by US president Barack Obama. All five permanent members - US, UK, France, China and Russia - and the 10 non-permanent members voted to pass the binding resolution that calls on countries to take steps to prevent and suppress support for terrorist groups like ISIS. This includes beefing up immigration controls to stop the movement of terrorist fighters across borders and allowing for the prosecution of those who continue to attempt to do so. The resolution also calls for countries to help build the capacity of states at the front line of this fight. At the same time, US air raids targeted ISIS oil installations in eastern Syria that have helped fund the group's brutal rise from rebel faction to alleged global threat.
Oct 3, 2014 - Isis released a video showing the beheading of British aid worker Alan Henning. It threatened American aid worker Peter Kassig with the same fate.
Nov 16, 2014 - A video of American aid worker Peter Kassig's beheading was released, making him the fifth Westerner whose execution is recorded and released by Isis.
Dec 15 to Dec 16, 2014 - A man declaring allegiance to Isis took hostages in a Sydney cafe. Two hostages died and the lone gunman, Man Haron Monis, was killed by police.
A hostage running towards a police officer outside Lindt cafe, where other hostages were held, in Martin Place, central Sydney, on Dec 15, 2014. -- PHOTO: REUTERS
Dec 19, 2014 - US Army Lieutenant General James Terry said there had been 1,361 air strikes against Isis to date.
Jan 13, 2015 - The US military's Central Command suspended its Twitter page after a group declaring sympathy for Isis hacked its social media accounts and posted internal documents.
The US Central Command's Twitter account page after the hacking. -- PHOTO: AFP
Jan 20, 2015 - Isis threatened to kill two Japanese hostages, Kenji Goto and Haruna Yukawa, unless a US$200 million ransom is paid.
Jan 24, 2015 - A video of Japanese hostage Kenji Goto is released. In the video, Goto appeared to be holding a photograph depicting the execution of his fellow Japanase hostage Haruna Yukawa. A voice which is said to belong to Goto then asked for the release of an Al-Qaeda-linked attempted female suicide bomber, Sajida al-Rishawi, in exchange for his freedom.
Source: Washington Post, BBC, Guardian, Institute for the Study of War, CNN
This article was first published on June 19, 2014 and updated on Jan 25, 2014