NEW YORK — Nearly three million Americans joined jihadist conflicts in the Middle East over the past decade, according to a massive joint investigation conducted by The Huffington Post, Salon and The New York Times.

Traveling in large groups by plane and even by boat, extremist groups have apparently infiltrated various cities and provinces in Iraq and Afghanistan since October 2001. It was unclear what caused such a large movement of terrorists into the region.

The foreign fighters, many of which commandeered military equipment like tanks and aerial bombers and appear in military-style fatigues, acquired combat training in remote areas of Washington state, North Carolina and various desert regions of California, experts tell Duffel Blog.

“Our studies confirm a startling fact: Many Americans have been radicalized right here at home,” wrote Kathleen Bellview, a professor of inductive history at Northwestern University. “And even more scary is that they return home from these far-off conflicts with uncontrollable madness. A minuscule fraction of one percent commit murder here at home. This is clearly public health issue number one.”

With the guerrilla wars beginning to wind down, many warn that the insurgents will return from overseas, be forced out of the terrorist service, and end up taking over local communities and enforcing hooah law.