ISIS is like a plantar wart on your toe: If you don’t cut all of it out, it will come back and start spreading again.

That appears to be what’s happening in Syria, where the terrorist group has surged attacks into areas that the Syrian regime and its Russian allies had controlled, a U.S. military spokesman said on Tuesday.

Previously, government officials confidently asserted that ISIS has lost 98% of its caliphate in Iraq and Syria since U.S.-led military operations began in August 2014 Now that ISIS is no longer a conventional army, the fight has become more complicated. The terrorist group is embracing asymmetric warfare tactics and can appear in areas thought cleared. The Syrian regime and Russians prefer to use brute force to solve all problems, but ISIS is attacking their weaknesses, not strengths.

Since December, ISIS has started to ramp up attacks against pro-regime forces west of the Euphrates River since December, said Army Col. Ryan Dillon. Unconfirmed media reports indicate that ISIS may have retaken neighborhoods in southern Damascus, he said.

“In the pro-regime area west of the Euphrates River, we have seen a resurgence – or, rather some ISIS elements coming back and attacking, with success, pro-regime forces,” Dillon told reporters during a Pentagon news conference.

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With recent gains in regime-held territory, ISIS currently controls “less than 10%” of its former territory, he said.

“We had said 98%, but as we’ve seen ISIS start to resurge in areas west of the Euphrates River, we’ll just keep it well over 90% of the territory that ISIS used to have has been retaken,” Dillon said.

However, after Tuesday’s briefing, Dillon backtracked on his comments about ISIS expanding into western Syria, telling Task & Purpose the 98% figure still remains accurate.

“Out of the about 100,000 square kilometers of territory that ISIS once held, there are still about 2,000 square kilometers that remain to be cleared,” Dillon said in an interview. “About 98% is where we stand on ISIS controlling territory from their high water mark.”

Dillon said he was unable to quantify how much territory west of the Euphrates ISIS may have captured. He also said he is unsure whether ISIS still controls neighborhoods in southern Damascus, adding: “I should not have said that they are retaking territory.”

None of the territory in Iraq or Syria that the U.S. military and its allies have cleared has fallen back to ISIS control, Dillon explained. Unlike the U.S.-led coalition, the Syrian regime and Russians do not deploy enough defensive forces to prevent ISIS fighters from retaking territory, he said.

If reports that ISIS retook territory in southern Damascus are accurate, it would mean that ISIS moved from the Euphrates across regime-held western Syria without being stopped, he said.

“Without that kind of emphasis on local security, you see what has happened on the west side of the Euphrates,” Dillon said. “As I look at the history of the fight against ISIS on the western side of the Euphrates – in Palmyra, as an example – the regime with Russian support took Palmyra; the Russians brought in a band and they played; then two weeks later, ISIS retook it, and that means they had to go back and kick them out again. This has happened more than once throughout western Syria.”

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