WASHINGTON — The Pentagon report that it has likely killed the Islamic State’s top military commander near the front lines in Syria is evidence of the terrorist group’s dire position in the war, Lt. Gen. Tony Thomas, who is nominated to lead Special Operations Command, told the Senate on Wednesday.

But the strategic victory was built on “extraordinary” battlefield losses among allied Syrian rebels in northeastern Syria who are at the center of the U.S. military’s renewed effort to train-and-equip friendly forces against the militants, Thomas told the Senate Armed Services Committee. More than 70 Syrian rebels were killed during the past month, he said.

Thomas’ testimony comes a day after the announcement that coalition airstrikes are believed to have killed Abu Omar al-Shishani, a 30-year-old Chechen, near the town of al-Shadadi, where the United States has focused strikes and cleared vast stretches of territory.

“I think it is telling, it speaks volumes about how dire their fight is that their senior military commander was in the thick of it at a relatively tactical location,” Thomas said.

The Pentagon on Wednesday could not confirm al-Shishani had been killed in the March 4 strike about 80 miles east of Raqqa, the terrorist group’s defacto capital.

Shishani, described as the Islamic State group’s “emir of war” or defense secretary, likely traveled to the front lines from Raqqa to rally his troops, who have taken heavy losses recently in battles with Syrian Democratic Forces, said Navy Capt. Jeff Davis, a Pentagon spokesman.

Thomas said the progress around al-Shadadi was possible by developing several surrogate rebel forces in northeastern Syria through the use of special operations forces. The effort has allowed the U.S. coalition to clear chunks of territory that are the combined size of New Jersey, Delaware and Rhode Island.

The U.S. trained and equipped rebels “have performed very, very well,” Thomas said. “Every time they’ve met their march objective on time or ahead of time and with pretty extraordinary losses.”

Special operators on the ground in Syria were able to confirm that 70-75 rebel fighters were killed in battles during the past month, Thomas said.

“They’re losing a lot of people to carry the fight against [the Islamic State], so I’m impressed with their tenacity,” he said.

The Obama administration’s original Syria train-and-equip program was viewed as an abject failure. During the summer, U.S. Central Command admitted only a handful of rebels had been produced by the $500-million program approved by Congress in 2014.

Now a new effort is underway as the role of special operations expands in Iraq and Syria. Last month, an Islamic State chemical weapons engineer was captured in Iraq by special operators, which appears to be part of the re-started Obama administration initiative.

Still, the war in Syria remains intense and complex, and the train-and-equip program still has skeptics in Congress.

Sen. Joe Manchin, D-W.V., said conditions in Syria are testing his past belief that sending American trainers and weapons to that country would make the United States safer.

“What I am hearing from the region further supports my belief that maybe it hasn’t,” he said.

Stars and Stripes reporter Corey Dickstein contributed to this story.

tritten.travis@stripes.com

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