On November 13, terrorists hit Paris with a series of coordinated attacks — France's deadliest since World War II. The Islamic State of Iraq and Syria (ISIS) claimed responsibility for the attacks, which killed at least 129 people, bringing a declaration of war from French President François Hollande and condemnation from world leaders. Who is ISIS and how has the militant group grown to wield so much influence? We've rounded up some of the best reporting on the origins of ISIS, their role in the Syrian civil war and ties to terrorist attacks across the world.

Editor's Note: Updated with new material.

Did we miss anything? Submit your suggestions in the comments.

Background on ISIS

How ISIS Works, The New York Times, September 2014

ISIS has a complex organizational structure and aspires to statehood. This is a crash course in how the group works to gain more territory through violence and the strategic takeover of oil assets.

What Washington Doesn't Get About ISIS, Politico, November 2014

How can the U.S. fight an enemy that it doesn't understand? This piece looks at some of the important things that U.S. officials misunderstand about ISIS, including tribal codes, the importance of history, and the scale of the threat that militant group presents.

What ISIS Really Wants, The Atlantic, March 2015

Graeme Wood writes on the origins and religious ideology of ISIS, and how a fundamental misreading of the differences between ISIS and al-Qaeda has led to 'dangerous decisions' by Western leaders.

More:Religious scholar on the 'phony' Islam of ISIS

Inside Isis Inc: The journey of a barrel of oil, Financial Times, October 2015

Crude oil is the biggest single source of revenue for ISIS. This Financial Times' special report details how ISIS finances its terror operations, who profits, and why it's difficult to disrupt.

Watch: a 5-minute history of Syria's war and the rise of ISIS, Vox, November 2015

From the first shots fired at Syrian protesters in 2011 to Russia's bombing of Syrian rebels fighting ISIS, this Vox video traces the evolution of Syria's civil war and ISIS's rise to power.

More: Guide to the Syrian Rebels, BBC, December 2013

The Age of Terror

Fear Itself: Learning to live in the age of terrorism, Washington Post, August 2004

Much has been made of the psychology of terror, but not about the psychology of the terrorized. In order to better understand the realities of living under imminent threat, Gene Weingarten journeyed to Madrid, "to ride the same train route that al Qaeda blew up," and then Jerusalem. "After 9/11, Americans are concerned enough by terror to be waging a costly war against it. But, by and large, the fear of terrorism has not seeped into our bones. We are new to this thing. The Israelis are not," Weingarten writes.

The Long Fuse of Obama's Anti-ISIS Strategy, Foreign Policy, May 2015

This is an examination of U.S. military operations against ISIS targets and the broader strategic problem that the militant group poses to the region and America's allies there.

Europe's Revolving-Door Prisons Compound Growing Terror Threat, ProPublica, June 2015

Europe is good at catching terrorists, but not so good at keeping them locked up. Sebastian Rotella examines the jihadi ties of two Charlie Hebdo attackers who cycled through French jails, and how Europe's sentencing polices haven't yet adapted to the reality of terrorism.

Balancing Security Against Free Speech, Washington Post, July 2015

Following an attack on tourists in Tunisia, ISIS claimed responsibility on Twitter. The group also promotes propaganda videos of mass killings on YouTube. Where the age of terror meets the age of social media, tech companies are left torn between free speech and security concerns.

Recent ISIS Attacks

Palmyra: historic Syrian city falls under control of Isis, The Guardian, May 2015

ISIS took control of the historic city of Palmyra, once a hub of the Silk Road, over a seven-day siege. According to Rami Abdul Rahman of the Syrian Observatory for Human Rights, the capture of Palmyra gave ISIS "almost complete control over the area from Palmyra to the Syrian-Iraqi border."

More:This is how the city of Palmyra looked before the attacks by ISIS.

ISIS Attacks Around the World, The New York Times, November 2015

ISIS has now declared provinces in eight countries beyond Iraq and Syria, and has extended its reach to North America, Europe and Asia. The New York Times details the rise in ISIS-related attacks and arrests over the last year.

How Paris Terror Attacks Unfolded, The New York Times, November 2015

On Nov. 13, 2015, terror struck Paris as more than 100 people were killed at random by terrorists. This video timeline of how the Paris Attacks unfolded from the bombings heard outside of the main sports stadium to the Bataclan Concert Hall.

Beirut, Also the Site of Deadly Attacks, Feels Forgotten, The New York Times, November 2015

The day before the Paris attacks, 43 people were killed in suicide bombings in Beirut, Lebanon. After the Paris attacks, Facebook allowed users to notify friends and family that they were OK through the platform's "Safety Check" feature. One Lebanese doctor wrote of the disparate response: "When my people died, no country bothered to light up its landmarks in the colors of their flag."

Continuing coverage of the Paris Attacks: BBC, CNN, New York Times and France24