A fighter of the Islamic State group waves a flag as they celebrate in the city of Mosul, Iraq, June 23, 2014. REUTERS/Stringer

When radicalized Germans head back home from fighting with the Islamic State group or other terror groups in the Middle East, their extreme ideologies tend to stick with them, a new report shows.

Just one in four jihadists who return to Germany after fighting with ISIS end up cooperating with law enforcement, while roughly half of those returning stay loyal to the terror groups they supported. The findings, reported Monday by the German newspaper Die Welt, were conducted by three German security agencies.

The report found that roughly 850 people left Germany to fight in Syria. Just 274 of those people —who were between the ages of 13 and 62 — returned to Germany after leaving and about half of them were still devoted to their extremist cause. Most were radicalized through friend groups, mosques or internet propaganda and about 61 percent were born in Germany, while other ISIS supporters came from Turkey, Syria, Russia or Lebanon.

“Radicalization happens predominantly in concrete social spheres,” the study states.

Radicalization in the Western world reached unprecedented levels last year with future fighters fleeing from all over, including the United States, to join the ISIS effort. Between July 2015 and June of this year, German authorities noted 49 people leaving to go fight with ISIS. The year prior saw as many as 100 people leaving each month.

National Security Advisor Susan Rice said Sunday on "CNN’s Fareed Zakaria" that more than half of the territory controlled by ISIS in Iraq has been taken back by the U.S.-led coalition and major cities would soon fall.

“The Iraqi Security Forces inside of Iraq have taken back about 55 percent of the populated territory that ISIL originally seized back in 2014,” Rice said, using an acronym for the terror group favored by the administration of President Barack Obama. “They have now, with our support and that of our 68-country coalition, encircled Mosul and they’re beginning to move into parts of Mosul.”