The Islamic State pledged over the weekend to bring an arduous fight to U.S.-led coalition forces battling to retake Raqqa, once the terrorist group's de facto capital in Syria.
An ISIS military commander warned Sunday in an interview with the group's English-language Rumiyah magazine that the Raqqa offensive will be "a fire that burns the Cross and its people, gives honor to the Islamic State, and raises its banner."
The unnamed commander threatened "a harsh lesson for the enemies of Allah," singling out the American-backed Syrian Democratic Forces, made up primarily of Arab and Kurdish fighters, according to SITE Intelligence Group, which tracks extremist propaganda.
ISIS also downplayed its recent defeat in Mosul, formerly a key stronghold for the group in Iraq, describing the nine-month battle as an exemplifier of the militants' "steadfastness, perseverance, and conviction in the face of disbelief."
The commander said jihadists will display similar resolve in Raqqa, stressing that ISIS will continue to operate regardless of defeat.
"There are no borders when establishing the Islamic State," the group wrote. "The determination to reside under Allah’s sharia and raise His word is not something restricted to any particular time or place."
The SDF launched the offensive to retake Raqqa in June. Col. Ryan Dillon, a spokesman for the U.S.-led coalition in Iraq and Syria, said on Thursday the SDF now controls 45 percent of Raqqa, though that figure has remained unchanged since the end of July.
Similar to its final days in Mosul, ISIS has turned to desperate tactics to stave off coalition advances. Dillon said last week a female suicide bomber camouflaged herself among hundreds of civilians fleeing the city before blowing herself up and killing several people.
Dillon said so far more than 80 percent of ISIS attacks against SDF forces have been carried out by hidden explosives.