The U.S. commander in the Middle East warned lawmakers Thursday about the risks of President Donald Trump’s plans to withdraw American forces from Syria and Afghanistan.

The Islamic State terrorist group is down to less than one square mile of territory in Iraq and Syria, but the group has made a “calculated decision” to lay low and remains a dangerous threat, Army Gen. Joseph Votel told the House Armed Services Committee.

Votel also said Russia reacted “positively” to the president’s December announcement of a planned U.S. troop withdrawal from Syria, saying Moscow views it as “an opportunity to fill the void.”

“It makes Russia a bigger player in the area. It puts Russia in the driver’s seat” in Syria, Votel said. “It solidifies their presence in the Middle East.”

Votel’s testimony contrasts substantially with recent remarks by Trump, who has celebrated the complete defeat of the Islamic State with only slight acknowledgement of the group’s persistent peril.