Key moments from the U.S.-led campaign in Iraq and Syria

U.S.-led forces have been carrying out airstrikes against Islamic State militants in Iraq and Syria since 2014, but have tried to avoid getting drawn into Syria’s ruinous civil war. On Thursday, President Trump authorized the deployment of cruise missiles against a Syrian air base in retaliation for an apparent poison-gas attack that U.S. officials say was carried out by President Bashar Assad’s military.

Aug. 20, 2012

Obama declares a ‘red line’ in Syria

President Obama warns Syria’s leaders that using chemical weapons would be a “red line” for the United States.

Aug. 21, 2013

Hundreds die in chemical attack

Hundreds are killed in a poison-gas attack targeting pro-rebel suburbs of the Syrian capital, Damascus. Obama considers a military response, but decides against it when President Bashar Assad’s government agrees to give up its chemical weapons.

An image released by the Syrian opposition Shaam News Network is said to show a woman mourning over a victim of a suspected gas attack in Ghouta, on the outskirts of Damascus. (Shaam News Network)

(DAYA AL-DEEN / AFP/Getty Images)

Jan. 14, 2014

Raqqah falls

Fighters loyal to Islamic State in Iraq and Syria take control of Raqqah after battling a coalition of rival rebel groups for the northern Syrian provincial capital.

June 10, 2014

Mosul falls

Islamic State in Iraq and Syria takes control of Mosul, Iraq’s second-largest city, before overrunning much of the northwest of the country.

June 18, 2014

Iraq seeks U.S. help

Iraq asks the U.S. to carry out airstrikes against Islamic State in Iraq and Syria.

June 29, 2014

Islamic State caliphate declared

Islamic State of Iraq and Syria announces in an audio recording that the militants have established a caliphate in eastern Syria and northwestern Iraq and are rebranding themselves as simply the Islamic State.

Islamic State fighters drive through Raqqah, capital of their self-declared caliphate in Syria. (Associated Press)

(Uncredited / AP)

Aug. 3, 2014

Thousands displaced

Islamic State drives Kurdish forces out of the Iraqi towns of Sinjar and Zumar, sending thousands of Yazidi civilians fleeing to the country’s semi-autonomous Kurdish zone.

Kurdish fighters check vehicles carrying Yazidi families fleeing from Islamic State in Iraq's Sinjar region. (Anadolu Agency / Getty Images)

Aug. 7, 2014

Obama authorizes airstrikes

Obama, saying that he is acting to avert a genocide, announces that he has authorized airstrikes against Islamic State militants in Iraq. He also confirms that U.S. cargo planes have dropped supplies to displaced civilians in the area of Mt. Sinjar who faced imminent starvation.

Bundles of meals parachute to the ground during a U.S airdrop over Iraq. (Department of Defense)

Sept. 5, 2014

U.S. calls for a coalition against Islamic State

Obama vows at a NATO summit to build an international coalition, including Sunni Arab states, to "degrade and ultimately destroy" Islamic State.

Aug. 19, 2014

James Foley beheaded

Islamic State posts video online showing the beheading of American journalist James Foley.

Islamic State released video said to show the beheading of American journalist James Foley. (Associated Press)

Sept. 2, 2014

Steven Sotloff beheaded

Obama orders 350 additional troops be sent to Iraq as video surfaces of the beheading of a second American journalist, Steven Sotloff.

Sept. 23, 2014

Airstrikes begin in Syria

The U.S.-led coalition launches its first airstrikes against Islamic State inside Syria.

Jan. 26, 2015

Kobani recaptured

Kurdish fighters, backed by U.S. firepower, drive Islamic State from the Syrian border town of Kobani after four moths of fighting.

Syrian Kurdish fighters celebrate their victory over Islamic State in Kobani. (European Pressphoto Agency)

March 31, 2015

Tikrit ‘liberation’ announced

Iraqi Prime Minister Haidar Abadi announces the "liberation" of Tikrit, the hometown of former strongman Saddam Hussein, although fighting and looting continue there for days.

Iraqi forces fire a rocket at Islamic State positions in Tikrit. (Khalid Mohammed / Associated Press)

May 20, 2015

Palmyra falls to Islamic State

Islamic State fighters seize Palmyra and proceed to destroy many ancient ruins near the fabled Syrian town.

Sept. 30, 2015

Russia begins airstrikes in Syria

Russian warplanes carry out their first airstrikes in Syria. Russian officials say the attacks in support of Assad's government target Islamic State positions, but Syrian opposition activists say the areas hit are in the hands of other rebel factions, including some backed by the U.S.

Dec. 28, 2015

Ramadi declared liberated

The Iraqi military declares that Ramadi has been liberated from Islamic State, although a general in the western province of Anbar tells reporters that the militants still control parts of the city.

Nov. 13, 2015

Sinjar recaptured

Iraqi Kurdish forces announce the recapture of the northern Sinjar region from Islamic State.

March 27, 2016

Palmyra back in government hands

Syrian government forces recapture Palmyra with the help of Russian air power, but will be driven out again in December.

June 17, 2016

Fallujah declared liberated

Abadi announces that the Iraqi city of Fallujah, long a hotbed of Sunni extremism, has “returned to the bosom of the nation." The fighting prompted a massive exodus from the city that overwhelmed aid workers.

Nov. 29, 2016

U.S. says coalition mistakenly targeted forces loyal to Assad

The U.S. military admits that coalition forces carried out an air raid that mistakenly killed dozens of Syrian-backed troops on Sept. 17 in the eastern Syrian town of Dair Alzour.

Oct. 16, 2016

Dabiq recaptured

Turkish-backed Syrian rebels retake Dabiq, dealing a symbolic blow to Islamic State, which believes the town will be the site of a doomsday battle between jihadis and their Western enemies.

Oct. 17, 2016

Mosul offensive begins

The Iraqi government, backed by U.S. airstrikes, launches a long-awaited campaign to drive Islamic State from Mosul, the group’s last major stronghold in the country.

Iraqi forces deploy in the area of Shurah, south of Mosul. (Ahmad al-Rubaye / AFP/Getty Images)

(AHMAD AL-RUBAYE / AFP/Getty Images)

Dec. 22, 2016

Syria declares victory in Aleppo

Syria’s government declares victory in Aleppo after the evacuation of opposition fighters from the city’s devastated eastern sector. The rebels had held parts of the city — their last major urban stronghold — for nearly four years.

March 17, 2017

Hundreds killed in apparent airstrike in Mosul

An apparent airstrike in western Mosul kills nearly 300 people. The U.S.-led coalition says it is investigating whether it was responsible; Iraqi officials blame Islamic State.

April 4, 2017

Dozens killed in apparent poison-gas attack

The U.S. and its allies accuse Assad’s government of carrying out an attack using a suspected nerve agent that killed about 80 civilians in the rebel-controlled province of Idlib. President Trump says the attack "crosses many, many lines" and was a consequence of Obama's "weakness and irresolution."

A Syrian doctor treats a child after a poison-gas attack in the town of Khan Sheikhoun. (Edlib Media Center)

(Uncredited / AP)

April 7, 2017

Cruise missiles launched into Syria

The U.S. fires 59 Tomahawk cruise missiles at a Syrian air base that officials said was used to launch the deadly poison gas attack on April 4.

The U.S. destroyer Porter launches a Tomahawk cruise missile in the Mediterranean Sea. (U.S. Navy)

(Ford Williams / AP)

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