Chronicling ISIS' reign of terror.
Western nations have made it harder for citizens to join ISIS in Syria, so some fighters are conducting operations at home.
Was the wave of recent attacks — from Turkey to Bangladesh, Baghdad to Medina — a sign of ISIS strength or weakness?
The Karakal Battalion was founded in 2000 as the country's first to mix male and female soldiers fighting side-by-side.
The 27-year-old New York man tells his story of joining and escaping the terror group.
NBC News' Richard Engel spoke one-on-one with an American who joined the terrorist group, then managed to escape.
The 27-year-old is now in federal custody and cooperating with authorities.
Teenagers are being turned into "weapons" by ISIS, triggering fears that they could slip back to the West to launch attacks.
Jaffrey Khan, Zakia Nasrin and Rasel Raihan lived in Ohio before joining the terror group.
They were from Silicon Valley and suburban Ohio and ended up in Syria.
Among thousands of ISIS recruits listed in the terror group's personnel files, there are names of Americans who've traveled to Syria.
ISIS personnel files obtained by NBC News revealed the identities of 15 Americans who left their country to fight for one of its most dangerous enemies.
ISIS recruitment as plummeted in 2016, and the militant group is struggling to pay fighters as coalition forces target its money.
By his own account, the man, who calls himself "Abu Mohammed," is an accomplice to murder and a thief.
Files on more than 4,000 fighters provide a deeper understanding of who signed up for ISIS.
ISIS leaders on the U.S. kill list have escaped, say critics, because the Obama administration will only let the CIA use its drones for surveillance.
Thousands of documents apparently leaked from inside ISIS paint a detailed picture of the terror group's personnel.
One woman has been battling ISIS for a year on her known as they threaten to wipe out her people: the Yazidis.
"Danger has always been part of my life," FEMEN leader Inna Shevchenko said.
ISIS started off the year with a bang — but 2015 has been a mixed bag for the terror group. Here's a look at how the year has played out.
Here's a look at how the year has played out for ISIS.
ISIS is transmitting hours of extremist propaganda into homes deep in one of Afghanistan's biggest cities for the first time.
At least one of the 34 countries listed by Saudi Arabia appeared surprised to be included in the group spanning the Middle East, Asia and Africa.
Abu Muhammad al-Adnani is the man behind the terror group's strategy of mass murder around the world.
While Rob Malley has decades of experience in national security, he's a lightning rod who has had his share of controversy concerning the Middle East.
ISIS still holds some 2,000 Yazidi women and girls, according to community leaders. Here some of the survivors and family members speak out.
Yazidi legislator Vian Dahkil is a desperate people's last and only hope.
For many Yazidi exiles in the U.S., this year's Thanksgiving feast will include a big side of gratitude for their deliverance from ISIS.
One man is fighting to chronicle the death of one of the world's oldest religions, the Yazidis, at the hands of one of its newest terror groups, ISIS.
Fian Ayub looked like she'd stepped out of the pages of a glossy Western bridal magazine — save for the rubble strewn behind her.
Mohammed Emwazi participated in numerous propaganda videos showing Westerners being beheaded.
The U.S. airstrike targeting the ISIS fighter nicknamed "Jihadi John" shows the U.S. has sophisticated intelligence and will serve as a morale blow.
The ISIS killer dubbed "Jihadi John" once vowed to achieve fame as a professional soccer player by the age of 30.
The families of Western hostages murdered by ISIS have expressed mixed feelings about news that Mohammed Emwazi was targeted by a U.S. airstrike.
"There is no vengeance, but there is accountability," a senior U.S. official told NBC News.
"This is the most important international police operation in Europe in 20 years," Italian anti-terrorism chief Giuseppe Governale said.
The beheading of seven civilians, including women and a child, by ISIS-linked militants in Afghanistan has raised fears that the terror group is tightening its grip.
ISIS seized control of Mosul in 2014.
Egypt's interior ministry said Aly Ashraf Hassanein al Gharabli masterminded the kidnap and murder of American oil worker William Henderson.
Seven civilians, including three women and a child, have been beheaded by suspected ISIS-linked militants in southern Afghanistan.
The double murder achieved its goal. It sent the message that, even here in the relative safety of Turkey, ISIS and its supporters can reach critics.
The White House was expected to announce the move later Friday.
Raqqa is Being Slaughtered Silently has been documenting ISIS abuses.
The rapper — born Denis Cuspert — had performed under the name "Deso Dogg" prior to joining ISIS.
The revelation came a day after U.S. Defense Secretary Ashton Carter said the U.S. may carry out more unilateral ground raids in Iraq to target ISIS militants.
A new video purports to show Thursday's raid in Iraq in which dozens of ISIS hostages were freed and an American commando was killed.
When presidents need to take out a terrorist or rescue hostages in a warzone, they turn to covert military units like Delta Force.
Authorities believe the account was created to lure in current law enforcement officers and collect their personal information.
IHS data showed the vast majority of attacks during the reporting period — just over 83 percent — were in Iraq and Syria.
The feds have arrested the hacker who allegedly gave personal data of government officials to ISIS.
Frustrated by what they see as America's failure to defeat ISIS, some Iraqi civilians want Russia to start bombing on their soil.
The rebel captain blames a lack of trainees and poor salaries for the "train and equip" program's failure.
These days Syrian Bashar al-Assad is so weak Russia and Iran are effectively running Syria.
After years of bringing hope to others, Syria's piano man has fled, his instruments destroyed by ISIS militants.
A video released by ISIS appeared to show more than a dozen of the terror group's fighters undergoing weapons training on American M16 rifles.
Iraqi refugees fleeing ISIS are living in fear swathes of humanitarian health services risked being axed because of a lack of international funding.
Two boys recount to NBC News their imprisonment and torture at the hands of ISIS.
Students from Iraq's University of Baghdad are using their summer break to learn how to fight ISIS.
It simply took a social media account for Mohammad Dakhlallah and his wife, Jaelyn Young, to connect with ISIS militants.
"If I can fight against them with my music, then my song is as powerful as or more powerful than their weapons," said Helly Luv.
Three women who spoke to NBC News were members of ISIS' morality police. They described life under the terror group's harsh rule in Syria.
Video obtained by NBC News and smuggled out of the ISIS stronghold of Raqqa offers a rare glimpse into life under the militants.
Are Russia and Iran set to abandon ally Syrian President Bashar Assad? NBC News' Chief Foreign Correspondent Richard Engel looks at what may happen.
Turkey's leader has offered a simple and resolute explanation for the simultaneous strikes: ISIS are terrorists and the PKK are terrorists.
Fleeing ISIS fighters have laid so many land mines that at least 15 villages around Hasakah, Syria, are now uninhabitable, a Kurdish commander said.
A man who dropped out of college to join ISIS said after being captured becoming a member of the extremist group was the worst decision he's made.
Robert Rose, a single dad from the South Bronx, is one of around 400 foreigners fighting with Kurdish forces against ISIS in Syria. This is his story.
"The more time on target, the better the estimate," a senior U.S. official told NBC News.
ISIS is all about creating an Islamic state — but to parents of kids who've joined the caliphate, the group's appeal often comes down to cash.
Iraqi Christians driven from their homes by ISIS have formed a militia and are fighting to retake their homeland from the extremists.
A bloody past and centuries of mistrust between two branches of Islam may doom Iraq's bid to crush ISIS.
A video statement issued by ISIS channels in Syria addressed the "tyrants of Hamas" and vowed to uproot the Palestinian organization.
Hundreds of northern Syrians attempt to find refuge in neighboring Turkey after fighting between Kurdish-led militia and Islamic State intensifies. Some 13,000 Syrians have already crossed into Turkey in the past week.
For Haider Oraibi, director of the Iraqi National Museum in Baghdad, the statues and relics being erased from Iraqi history have great significance.
One year after a caliphate was declared spanning Syria and Iraq, there is little to celebrate — unless you're ISIS.
There is a heightened state of concern among U.S. intelligence and law enforcement about an ISIS-inspired attack through the July 4 weekend.
A new study shows that domestic attacks, not fighting overseas, is increasingly the goal of those arrested in ISIS-linked cases.
Kurdish forces say they seized a military base from ISIS fighters in northern Syria.
Shia militias are pushing ISIS back in the Anbar province, where with Iran's help, they aim to take back Iraq from the terror group.
NBC News' Bill Neely watched fighters from Iraq's Badr organization as they prepared to face ISIS in the battle for Ramadi.
The Afghan Taliban is struggling to maintain a unified facade amid reports of splits within the group.
The Taliban has warned ISIS militants to stay out of Afghanistan in a rare open letter to the extremists that have conquered swathes of the Middle East.
American citizen Keith Broomfield, who was killed fighting ISIS, believed it was "God's will" that he go to Syria, his mother told NBC News.
"We believe that the international community cares about the stones statues much more than about to us," said Nasser Al-Saer.
A U.S. diplomat's assertion that airstrikes had killed 10,000 ISIS fighters has raised questions about how the government compiled the estimate.
ISIS has conquered a key city some 70 miles from Baghdad. What now stands between the extremists and Iraq's capital? Analysis by NBC News' Bill Neely.
For the U.S. to stomp out ISIS, taking down its financing appears just as important as taking out the group's operations in air attacks.
Foreign militants fighting and recruiting under the ISIS flag have moved into towns and villages in northern Afghanistan and begun terrorizing locals.
A spate of new incidents has sparked concern that the terror group's popularity is spreading well beyond Syria and Iraq.
A new study says U.S. residents accused of supporting the terror gang are drawn in by the fantasy, and not necessarily an urge to attack Americans.
Militiamen fighting ISIS with the Iraqi Army and Kurdish forces are accused of kidnapping, killing and driving civilians from their homes.
ISIS has hundreds of millions of dollars and earns cash from oil and extortion, but spends it fast on running a caliphate.
A group of Americans fights to take back "cities that hundreds of Marines and soldiers died for."
Kurdish forces in the north and Shiite militia in the south are squeezing the Islamists on two fronts.
A new video purports to show military-style training for children in Syria.
Aid workers in northern Iraq are tirelessly helping to rehabilitate Yazidi women who were taken hostage and held as slaves by ISIS.
The horrific execution tactic is the latest in a string of brutal punishment methods applied by ISIS under its strict interpretation of Islamic — or shariah — law.
One Yazidi woman, held captive by ISIS, recalls members of the terrorist organization calling prisoners "infidels" and saying "we will do what we want with you."
American ISIS hostage Kayla Mueller is dead, the aid worker's family and the White House said Tuesday.
ISIS in Mosul has been attempting to bolster its ranks by forcing Iraqi young men to conscript and become jihadi fighters, a resident said.