 -- Six months ago U.S. intelligence analysts warned in an eerily prescient assessment that a failed Belgian terror plot might foreshadow a new capability by ISIS to conduct complex, deadly attacks in the heart of Europe -- exactly like what happened in Paris last week.

In the May report, the Department of Homeland Security’s Intelligence and Analysis directorate even singled out Abdelhamid Abaaoud, the Belgian who organized a purported jihadist cell in the Brussels neighborhood of Molenbeek last January and who now has emerged as the purported “mastermind” of the Paris attacks.

The nine-page I&A report for American law enforcement said Abaaoud and his collaborators in Belgium appeared to be part of a new effort more dangerous than the well-known ISIS strategy to inspire unskilled wannabe jihadis through social media to commit lone-wolf strikes.

"I&A assesses that the plot disrupted by Belgian authorities in January 2015 is the first instance in which a large group of terrorists possibly operating under ISIL direction has been discovered and may indicate the group has developed the capability to launch more complex operations in the West," stated the DHS report last May, marked for official use only and using an alternate name for ISIS.

Previously it was al Qaeda, not ISIS, which was known for infiltrating secret cells of operatives into the West to conduct complex, simultaneous attacks such as what transpired in Paris on Friday night.

"I&A judges that the threat from ISIL plots involving multiple operatives may grow, but are more likely to occur in Europe -- where several recruitment networks have been disrupted, and several returning fighters have already demonstrated the ability to conduct attacks -- than in the United States given the different operating environments, number of European foreign fighters currently in theater and Europe’s geographic proximity to the conflicts in Syria and Iraq," the DHS report said.

The DHS document, first reported by CNN today, was posted on the Public Intelligence whistleblower website. While two of his extremist comrades were killed in the January shootout with police, Abaaoud reportedly escaped and reappeared in Syria in February in an ISIS magazine, bragging that he had slipped the law enforcement dragnet. Now he’s wanted for his purported key role in the Paris attacks.

Earlier this week, U.S. officials told ABC News ISIS has developed a new unit within the organization to plot and carry out external operations against the West.

The I&A analysts, who examine intelligence about U.S. homeland threats largely collected by other American law enforcement and intelligence agencies, said the "complex, centrally-planned plotting in Belgium" was a departure from previous efforts involving "more-simplistic attacks by ISIL-inspired or directed individuals" and "could occur with little to no warning."

‘We Have Disrupted a Certain Number of Attacks’ in France

U.S. officials today would not say whether the U.S. intelligence assessment of the Belgian cell was passed to the French government, but a DHS spokesperson said that in general, “DHS routinely shares information and collaborates with our international, federal, state and local law enforcement, intelligence and homeland security partners on the latest threats.” Another American official called intelligence sharing on threats with France and the rest of Western Europe "very robust."

President Obama said Sunday that "no specific" intelligence could have led the U.S. to warn France about the actual attack Friday.

Last month, CIA Director John Brennan told a security conference, “I do think that the sharing of information today is better than it's ever been before -- but it still is imperfect.”

France's top intelligence official disclosed that the security partnership between America and its oldest ally had disrupted recent terrorist plots, though without revealing any details, at the same Oct. 27 conference put on by the Center for Cyber and Homeland Security at George Washington University and CIA.

"During the last month, we have disrupted a certain number of attacks on our territory by our own means or thanks to the cooperation we have with the CIA, NSA, and so on. So it works," said Bernard Bajolet, director of the French Directorate General for External Security (DGSE).

But Bajolet, who estimated that 500 Frenchmen are fighting jihad in Syria, also presciently warned that France and its allies battling ISIS with airstrikes in Syria and Iraq won't always be able to prevent terrorist strikes at home.

"There are threats that are very difficult to detect especially when they come from our own territory," he said.

Tuesday ISIS fighters threatened to strike Washington, D.C., but most American counter-terrorism assessments have concluded that ISIS does not have the capability to launch attacks similar to Paris inside the American homeland.