WASHINGTON--The United States is poring over a vast trove of new intelligence about Islamic State fighters who have flowed into Syria and Iraq and some who then returned to their home countries, information that American officials say could help fight militants on the battlefield and prevent potential plotters from slipping into Europe.

American-backed Syrian Kurdish and Arab militias have seized more than 10,000 documents and 4.5 terabytes of digital data in recent weeks while fighting insurgents in Manbij in northern Syria, near the Turkish border, a major hub for Islamic State fighters entering and leaving Syria, American officials said.

An initial American review of the material offers new clues about “foreign fighters, the networks, where they’re from,” according to Brett McGurk, President Obama’s special envoy for combating the Islamic State. Other officials said the information included the fighters’ identities, countries of origin, routes into Syria and the illicit networks that recruited and ferried them to the region. Those details are being shared with allies to help stanch the flow of militants.

“We want to make sure that all that information is disseminated in a coherent way among our coalition partners,” Mr. McGurk said last week, during a meeting of foreign and defense ministers in Washington, “so that we can track the networks from the core and all the way to wherever the dots might connect, whether that is in Europe or in North Africa or Southeast Asia.”

It is the largest single trove seized in the fight against the Islamic State since Delta Force commandos raided the home of a top Islamic State financier in eastern Syria in May 2015. That operation carried off laptops, cellphones and other materials that led to airstrikes against top terrorist leaders and opened a valuable window into how the group manages its finances, brokers hostages for ransom and delegates duties within its self-proclaimed caliphate.

The latest seizure comes as a failed coup in Turkey has cast new doubts on that country’s ability and willingness to deploy military and other security forces to seal its long border with Syria.

Many senior Turkish officers have been detained in a post-coup crackdown, leading American officials to worry that Turkish counterterrorism efforts will be weakened.

American intelligence agencies estimate that nearly 43,000 fighters from more than 120 countries, including 250 Americans among 7,400 Westerners, have gone or tried to go to Syria and Iraq since 2011.

While Turkey’s border tightening and other intelligence and law enforcement measures have by some estimates cut in half the monthly flow into Syria and Iraq, American analysts say as many as 500 to 1,000 fighters a month are still pouring in, with hundreds of others heeding the Islamic State’s call to go to affiliates in Libya or Afghanistan instead, or remain at home and carry out attacks from there.

Earlier this month, a top United Nations official said that nearly 30,000 of those foreign fighters remained in Syria and Iraq, far more than Western intelligence agencies had estimated. The official, Jean-Paul Laborde, a United Nations assistant secretary general and head of its counterterrorism committee, told reporters in Geneva that as the Islamic State loses territory in Iraq and Syria, “we are seeing them return, not only to Europe but to all of their countries of origin, like Tunisia, Morocco.”

American military and intelligence analysts are combing through the documents and electronic data recovered in Manbij, hoping to add to their growing knowledge of the rosters of Islamic State fighters and to help identify, locate and attack fighters in Syria and Iraq.

In a speech Wednesday at Fort Bragg, N.C., Mr. Carter described Manbij as “a key transit point for external plotters threatening our homelands. And there we’re already beginning to gain and exploit intelligence that’s helping us map their networks of foreign fighters.”

Another use of the documents is, as Mr. McGurk said, to alert foreign intelligence and counterterrorism services across Europe, the Mideast and North Africa, even as a spate of terrorist attacks in France and Germany, some apparently inspired by the Islamic State, have roiled Europe.Any information from the Manbij trove would augment the activities of a sensitive intelligence-coordination center at a military base in Jordan called Operation Gallant Phoenix.

The latest trove of documents was collected in various locations in the region around Manbij, where Syrian Kurdish and Arab fighters, backed by American Special Operations commandos, have battled Islamic State fighters at a crucial junction between the Turkish border and Raqqa, the Islamic State’s de facto capital in Syria.

American officials express confidence that the latest cache will yield similar insights. (Source: The New York Times)

Story Date: July 29, 2016