(CNN)Here's a look at Islamic State in Iraq and Syria (ISIS).
Started as an al Qaeda splinter group.
Started as an al Qaeda splinter group.
The group is implementing Sharia Law, rooted in eighth century Islam, to establish a society that mirrors the region's ancient past.
ISIS is known for killing dozens of people at a time and carrying out public executions, crucifixions and other acts.
ISIS uses modern tools like social media to promote reactionary politics and religious fundamentalism. Fighters are destroying holy sites and valuable antiquities even as their leaders propagate a return to the early days of Islam.
In 2014, ISIS controlled more than 34,000 square miles in Syria and Iraq, from the Mediterranean coast to south of Baghdad. At the end of 2016, ISIS territory had shrunk to about 23,320 square miles, according to IHS Jane's.
In 2015, ISIS was believed to be holding 3,500 people as slaves, according to a United Nations report. Most of the enslaved were women and children from the Yazidi community, but some were from other ethnic and religious minority communities.
ISIS's revenue comes from oil production and smuggling, taxes, ransoms from kidnappings, selling stolen artifacts, extortion and controlling crops.
Abu Bakr al-Baghdadi.
Abu Bakr al-Baghdadi.
Is reportedly based in Syria.
Al-Baghdadi was detained for several months in Camp Bucca, which was a US-run prison in southern Iraq. He was released in 2004.
2004 - Abu Musab al-Zarqawi establishes al Qaeda in Iraq (AQI).
2004 - Abu Musab al-Zarqawi establishes al Qaeda in Iraq (AQI).
2006 - Under al-Zarqawi, al Qaeda in Iraq tries to spark a sectarian war against the majority Shia community.
June 7, 2006 - Al-Zarqawi is killed in a US strike. Abu Ayyub al-Masri takes his place as leader of AQI.
October 2006 - Al-Masri announces the creation of Islamic State of 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 al-Masri are killed in a joint US-Iraqi operation.
April 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 Islamic State in Iraq and the Levant (ISIL or ISIS).
January 2014 - ISIS takes control of Falluja.
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, according to London-based monitoring group Syrian Observatory for Human Rights.
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.
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 Pentagon announces the United States is sending an additional 300 troops to Iraq, bringing the total US forces in Iraq to nearly 800. Troops and military advisers are sent to Iraq to support Iraqi security forces and help protect the US Embassy and the airport in Baghdad.
July 2014 - ISIS takes control of Syria's largest oilfield and seizes a gas field in the Homs Province, storming the facility and killing dozens of workers. Militants conquer a 90-mile stretch of Syrian towns, from Deir Ezzor to the Iraq border. In Mosul, they blow up Jonah's tomb, a holy site dating back to the 8th century BC.
August 6, 2014 - ISIS fighters attack the northern Iraqi town of Sinjar, home of a religious minority group called the Yazidis. More than 30,000 Yazidi families are stranded in the Sinjar Mountains. A Yazidi lawmaker says that 500 men have been killed, 70 children have died of thirst and women are being sold into slavery.
August 8, 2014 - Two US jet fighters bomb ISIS artillery units in Iraq. President Barack Obama authorizes "targeted airstrikes" if needed to protect US personnel and prevent potential genocide of minority groups.
August 19, 2014 - ISIS posts a video showing the beheading of US journalist James Foley, missing in Syria since 2012.
September 2, 2014 - ISIS releases a video showing the beheading of US journalist Steven Sotloff. Sotloff's apparent executioner speaks in the same British accent as the man who purportedly killed Foley.
September 11, 2014 - The CIA announces that the number of people fighting for ISIS may be more than three times the previous estimates.
September 13, 2014 - ISIS militants post a video showing the apparent execution of British aid worker David Haines.
October 3, 2014 - ISIS releases a video showing the apparent beheading of British hostage Alan Henning.
November 3, 2014 - The Iraqi government announces ISIS militants have killed 322 members of a Sunni tribe in a series of executions.
November 14, 2014 - The UN Independent International Commission of Inquiry on Syria concludes that ISIS has committed war crimes and crimes against humanity.
January 22, 2015 - US diplomatic officials say that coalition airstrikes have killed an estimated 6,000 ISIS fighters.
January 24, 2015 - A photo and audio released by ISIS appear to show the beheaded body of Japanese hostage, Haruna Yukawa.
January 31, 2015 - ISIS releases a video that appears to show the decapitated body of a second Japanese hostage, Kenji Goto.
February 3, 2015 - Video and still images posted by ISIS apparently shows Jordanian pilot Moath al-Kasasbeh being burned alive while locked in a cage.
February 5, 2015 - Jordanian fighter jets carry out airstrikes over Syria, reportedly hitting ISIS training centers as well as arms and ammunition depots in Raqqa. The next day, ISIS claims that the airstrikes killed American hostage Kayla Jean Mueller. The post contains a picture of a collapsed building and ISIS claims Mueller is buried in the rubble.
February 10, 2015 - Mueller's family announces she is dead, after receiving confirmation from ISIS, including a photo of her wrapped in a burial shroud.
February 11, 2015 - President Obama asks Congress to formally authorize use of military force against ISIS.
February 15, 2015 - ISIS posts a video in which militants appear to behead more than a dozen Egyptian Christians on a Libyan beach. The next day, Egyptian warplanes strike ISIS targets in Libya.
February 22, 2015 - ISIS releases a video that appears to show at least 21 Kurdish Peshmerga fighters in cages carried down Iraqi streets.
February 26, 2015 - Jihadi John, the disguised man with a British accent who appears in ISIS videos as the executioner of Western hostages, is identified as Mohammed Emwazi, a Kuwaiti-born Londoner. On the same day, ISIS releases a video of its fighters destroying antiquities at the Mosul Museum.
March 2015 - ISIS posts images of a man being thrown off a building in Raqqa, Syria. He had been accused of being gay. There are at least a half dozen documented cases of ISIS killing men accused of being gay.
March 1, 2015 - ISIS releases 19 Christian prisoners. All but one are from a group of 220 Assyrians captured in northern Syria.
March 7, 2015 - In an audio message purportedly from Boko Haram leader Abubakar Shekau, the Nigeria-based radical Islamic group pledges allegiance to ISIS. Days later, an ISIS spokesman claims the caliphate has expanded to western Africa.
March 12, 2015 - Iraqi forces retake most of Tikrit. In western Iraq, ISIS blows up the Iraqi army headquarters north of Ramadi, killing at least 40 Iraqi soldiers.
April 8, 2015 - According to Iraqi Kurdistan officials, ISIS releases more than 200 Yazidi women and children, as well as the ill or elderly.
April 19, 2015 - ISIS releases a video that appears to show militants beheading two groups of prisoners in Libya. The Ethiopian government confirms that 30 of the victims were Ethiopian citizens.
May 16, 2015 - A key ISIS leader is killed during a US Special Operations raid in Syria, according to US officials. His wife is captured and the raid yields significant intelligence on ISIS's structure and communications.
May 17, 2015 - ISIS seizes control of Ramadi, the largest city in western Iraq, after government security forces pull out of a military base.
May 21, 2015 - ISIS takes control of Palmyra, an ancient Syrian city that is a UNESCO World Heritage Site. According to the Syrian Observatory for Human Rights, it was the last Syria-Iraq border crossing under control of Syrian troops.
June 14, 2015 - A British teen, Talha Asmal, is reportedly one of four ISIS suicide bombers who attack the headquarters of a Shia militia group in Iraq, killing at least 11. Before the bombing, ISIS posted photos of Asmal, 17, posing next to their black flag on social media. According to the BBC, Asmal left England in March to join the Islamic fundamentalists.
June 19, 2015 - The State Department issues its annual terrorism report, declaring that ISIS is becoming a greater threat than al Qaeda. The frequency and savagery of ISIS attacks are alarming, according to the report.
June 24, 2015 - The Syrian government reports that ISIS militants have destroyed two Muslim holy sites in Palmyra. The group attacked a 500-year-old shrine and a tomb where a descendent of the Prophet Mohammed's cousin was reportedly buried.
June 26, 2015 - A gunman kills at least 38 people at a beachfront Tunisian hotel, and a bomb kills at least 27 people at a mosque in Kuwait. ISIS claims responsibility for the attacks.
July 1, 2015 - ISIS launches simultaneous attacks on five Egyptian military checkpoints, reportedly killing 17 Egyptian soldiers and injuring 30 others. According to the Egyptian military, 100 terrorists are killed in the fighting.
July 4, 2015 - The Syrian Observatory for Human Rights reports it has received a video showing ISIS militants executing 25 captives in Palmyra.
July 17, 2015 - As Iraqis celebrate Eid al-Fitr, a holiday marking the end of the fast for Ramadan in Khan Bani Saad, ISIS detonates an ice truck in a crowded marketplace, killing at least 120 people and wounding at least 140 more.
August 2015 - ISIS destroys antiquities in Palmyra, including the nearly 2,000-year-old Temple of Baalshami. UNESCO, the UN's cultural organization, calls the destruction of the temple a "war crime."
November 12, 2015 - The Pentagon announces that it has conducted a remote control drone strike targeting Mohammed Emwazi, also known as "Jihadi John." ISIS later confirms the death of Emwazi.
November 12, 2015 - Two suicide bombs hit the Bourj al-Barajneh district of southern Beirut, killing more than 40 people and wounding hundreds. ISIS claims responsibility for the attack.
November 13, 2015 - After a two-day battle, the Peshmerga Iraqi Kurdish military force declares victory in liberating the Iraqi town of Sinjar from ISIS. The battle was backed by the US coalition air power.
November 13, 2015 - Three teams of gun-wielding ISIS suicide bombers hit six locations around Paris, killing at least 129 people and wounding hundreds.
December 10, 2015 - A spokesman for the US-led coalition comfirms that ISIS Finance Minister Abu Saleh was killed in an airstrike in late November in Iraq.
December 28, 2015 - Iraqi troops retake the city of Ramadi from ISIS and raise the Iraqi flag on top of the government compound in the city's center, according to an Iraqi military spokesman.
January 24, 2016 - ISIS releases a video that purports to show final messages from the Paris attackers.
February 21, 2016 - Multiple attacks in Homs and southern Damascus kill at least 122 and injure scores, according to Syria's state-run SANA news agency. ISIS claims responsibility.
March 22, 2016 - Attacks on the airport and a subway station in Brussels, Belgium kill more than 30 people and wound about 270 more. ISIS claims its "fighters" launched the attacks.
March 25, 2016 - The Pentagon confirms that US military forces have killed ISIS' finance minister, Abd al-Rahman Mustafa al-Qaduli. While Defense Secretary Ash Carter would not give details on the operation, another US official told CNN that special operations forces intended to capture al-Qaduli alive, but the plan was modified at the last moment.
June 26, 2016 - A senior Iraqi general announces on state TV that the battle for Falluja is over, as Iraqi troops retake the final ISIS holdout in the city.
June 28, 2016 - At least 44 people die and more than 230 are injured when three attackers armed with firearms and explosives arrive at Turkey's Istanbul Ataturk Airport in a taxi, then open fire before blowing themselves up. US officials believe the man who directed the three attackers is Akhmed Chatayev, a terrorist from Russia's North Caucasus region and a well-known ISIS lieutenant.
July 1-2, 2016 - Attackers invade the Holey Artisan Bakery cafe in a diplomatic enclave of Dhaka, the capital of Bangladesh. Gunmen kill 20 hostages and two police officers before authorities raid the restaurant and end the nearly 11-hour standoff. ISIS claims responsibility for the attack, but Bangladeshi officials say the attack was carried out by homegrown militants. US officials focus on ISIS as the perpetrator after photos purportedly showing the inside of the cafe and dead hostages are posted on an ISIS-affiliated website.
July 3, 2016 - A suicide car bomb detonates in a busy shopping district in Baghdad, killing at least 292 people and injuring another 200. It is the deadliest single attack in Iraq since 2003. ISIS claims responsibility.
August 30, 2016 - According to a statement from the terror group and its Amaq news agency, ISIS spokesman Abu Muhammad al-Adnani has been killed in the area of Aleppo, Syria. Without confirming al-Adnani's death, the Pentagon confirms that coalition forces conducted an airstrike in al Bab, Syria, targeting him.
September 16, 2016 - Pentagon Press Secretary Peter Cook says a US air strike targeted and killed Wael Adel Salman, aka Abu Muhammad al-Furqan, ISIS's chief spokesman, just days after killing his predecessor. Salman was the ISIS minister of information, responsible for overseeing the production of "terrorist propaganda videos showing torture and executions," Cook says.
October 17, 2016 - Iraqi Prime Minister Haider al-Abadi makes a televised statement announcing the start of the mission to retake the key city of Mosul, the last remaining ISIS stronghold. He says a coalition of about 100,000 troops will play a role in the operation, though some will have a holding role behind the front lines or other support roles. The force includes about 54,000 members of the Iraqi Security Forces, 40,000 Kurdish Peshmerga fighters, 14,000 members of paramilitary units - 9,000 Sunni fighters and 5,000 from other minorities including Christians, Turkmen and Yazidis - and approximately 500 US service members who will serve mainly in a logistical capacity. US military officials have estimated up to 5,000 ISIS fighters are in Mosul, but the terror group's supporters say there are 7,000.
October 24, 2016 - Suicide bombers attack sleeping cadets at a police training academy in Pakistan, killing 61 and injuring 117. ISIS claims responsibility, releasing a photo of the three purported attackers, but Pakistani military leaders say they believe a Pakistan-based group, Lashkar-e-Jhangvi carried out the attack.
April 9, 2017 - ISIS claims responsibility for two deadly bombings targeting Coptic Christian churches on Palm Sunday in Egypt. At least 49 people were killed and 119 others injured in the blasts.
April 13, 2017 - The US military drops its most powerful non-nuclear bomb on an ISIS compound in Afghanistan. An Afghan official later tells CNN that 94 militants were killed in the blast.
May 26-28, 2017 - More than 200 civilians are murdered by ISIS militants in Mosul, according to the UN.
May 26, 2017 - Buses carrying Coptic Christians in Egypt are attacked by assailants, who fatally shoot at least 29. ISIS claims responsibility.
July 10, 2017 - Iraqi Prime Minister Haider al-Abadi declares that Mosul has been recaptured from ISIS.
October 17, 2017 - ISIS loses control of its self-declared capital, the Syrian city of Raqqa. US-backed forces fighting in Raqqa say "major military operations" have ended, though there are still pockets of resistance in the city.
December 9, 2017 - The Iraqi military says it has "fully liberated" all of Iraq's territory of "ISIS terrorist gangs" and retaken full control of the Iraqi-Syrian border. The campaign to eradicate the Islamic State took more than three years and about 25,000 coalition airstrikes.