WASHINGTON — An American-backed ground offensive to wipe out the last pockets of Islamic State fighters in eastern Syria has been reignited over the past month in an attempt to beat back the militants’ ability to wage guerrilla attacks.

The mission against the Islamic State has been invigorated by the return of top Kurdish commanders, a surge in French commandos, the arrival of Navy fighter jets and some secret sleuthing by Iraqi spies.

But the campaign may have only little more than six months to hunt down the few hundred fighters — not enough time to extinguish a threat that is quickly moving underground.

The new momentum remains imperiled by President Trump’s on-again, off-again threat to withdraw some 2,000 American troops in Syria, including hundreds of Special Operations advisers and commandos.