Kurdish-led Syrian Democratic Forces (SDF), backed by U.S.-led coalition airstrikes, intensified their efforts to obliterate the last vestige of the Islamic State’s (ISIS/ISIL) so-called caliphate in eastern Syria near the Iraqi border, launching their latest ongoing offensive against the jihadis on Sunday.

In recent months, U.S.-backed local forces have reduced the so-called caliphate that once spanned swathes of Syria and neighboring Iraq down to a sliver of land atop caves and tunnels along the Iraqi border. However, ISIS fighters have put up a tough fight, refusing to surrender.

On Sunday, forces from the Kurdish-Arab SDF alliance launched the latest offensive to wipe out the group’s last enclave as U.S.-led coalition airstrikes targeted ISIS weapon caches.

Mustafa Bali, an SDF official, told Reuters on Sunday that “direct and fierce” clashes were underway.

The assault by the SDF aims to wipe out the last remnants of the ISIS territorial caliphate in the eastern Syrian village of Baghouz that sits near the Iraqi border.

Noting that civilians are no longer emerging from the enclave — one of the factors responsible for slowing down the anti-ISIS offensive — Bali said, “The military operations have started. Our forces are now clashing with the terrorists, and the attack started.”

The evacuation of civilians, mainly the wives and children of ISIS jihadis, have reportedly impeded the operations against ISIS.

U.S.-backed SDF forces have been fighting to clear the last ISIS stronghold for weeks. Nevertheless, ISIS has riddled its last bastion with defensive tunnels and mines and is also using civilians as human shields, effectively preventing the local forces from declaring the group’s territorial defeat.

“Tens of thousands of people have streamed out of the shrinking territory held by Isis over the last months. Bali said more than 4,000 militants had surrendered to the SDF in the past month. …The fate of the Isis leader, Abu Bakr al-Baghdadi, remains a mystery,” Reuters notes.

Although U.S.-backed local forces have nearly taken back all of the territory once held by ISIS, American military and intelligence officials have repeatedly warned that the group has taken an underground guerrilla form that remains a threat to American interest in the Middle East and beyond.

Task & Purpose reports:

Islamic State is trying to mount a comeback, and the Iraqi military is trying to root out sympathizers and sleeper cells still embedded in the extensive territory the group once controlled. By many accounts, the government is failing to contain a budding insurgency, the sort of resilient, underground enemy that has outlived governments around the world. Stripped of its territory — which once encompassed a third of both Iraq and Syria — Islamic State has reverted to its roots, using small, self-contained teams of operatives to conduct small-scale attacks and assassinations and rebuild its smuggling and ransom operations.

In an interview with Breitbart News, top SDF leader also warned about the presence of ISIS “sleeper cells” across Syria.

U.S. President Donald Trump declared the ISIS caliphate “defeated” in announcing U.S. plans to pull out of Syria in December.

On Sunday, however, Trump’s National Security Adviser John Bolton conceded that the terrorist group remains a threat, adding that it is “growing in other parts of the world.”

Bolton told ABC News:

The president has been, I think, as clear as clear can be, when he talks about the defeat of the ISIS territorial caliphate. He has never said that the elimination of the territorial caliphate means the end of ISIS in total. We know that’s not the case.

ISIS jihadis are “scattered still around Syria and Iraq, and that ISIS itself is growing in other parts of the world. The ISIS threat will remain,” he added.

At the end of the year, Breitbart News acknowledged that thousands of ISIS jihadis remained active outside of Iraq and Syria despite the demise of the group’s caliphate

President Trump has agreed to leave behind a residual American force in Syria to ensure ISIS’s lasting defeat. The Trump administration has also stressed that an estimated 5,000 U.S. troops will remain in Iraq with the capability to enter Syria if necessary.