Photos and video footage that surfaced on Twitter and YouTube this week appear to show a convoy of flatbed trucks loaded with U.S.-made MRAP, M-ATVs, and up-armored bulldozers in Syria, Military Times reports.

The Kurdish activists who posted the images on social media on July 18 claim the convoy was bound for the U.S.-backed Syrian Democratic Forces, or SDF, in Raqqa. The footage was purportedly taken while the convoy was passing through Qamishli, a city in northeast Syria situated near the borders of Turkey and Iraq.   

Guardian armored trucks and U.S. up-armored Humvees are included in the coalition aid to the SFD, and according to the Defense Department’s fiscal year 2018 request for funds for train-and-equip program for Syrian partner forces, armored bulldozers are also included in aid to “vetted” Syrian groups, Military Times reports.

“Up-armored vehicles have been delivered to the SDF and [Syrian Arab Coalition] as part of our existing authorities to enable them,” a spokesperson for Operation Inherent Resolve told Task & Purpose in an email. (The Syrian Arab Coalition, or SAC, is the Arab component of the SDF.) “Specifically, these vehicles will help them contend with ISIL’s IED threat in their current operation, and as they move to isolate Raqqah.”

However, the OIR spokesperson explained that M-ATVs and MRAPs are “not part of the package that is divested to the SDF.” And, as Military Times notes, neither are the Common Remotely Operated Weapon Station, or CROWs system, which appear mounted on the M-ATVs featured in the photographs.

“These vehicles are for use by the Coalition to protect our forces from IEDs,” the spokesperson said.

The U.S. had been directly arming Kurdish militants in northern Syria in recent months against the objections of Turkey, and assisting the SDF now accounts for the bulk of the Pentagon’s efforts on the ground in Syria after President Donald Trump decided this week to end a covert CIA program to arm and train moderate rebel groups. Turkey perceives the possible establishment of an autonomous Kurdish state south of its border as a direct threat to its national security.

The Syrian Kurds fighting with the People’s Protection Units, or YPG, form the backbone of the SDF, which continues to play a central role in the U.S.-led coalition’s campaign to wrest Raqqa, ISIS’s de facto capital, from militant control. Raqqa is seen as the last major battle in the years-long campaign to destroy ISIS under the banner of Operation Inherent Resolve

Given the amount of coalition firepower and its recent success in the former ISIS stronghold of Mosul, it is widely expected that Raqqa will fall. However, the images of heavily armored American combat vehicles entering Syria seem to bolster recent reports that the fight is proving more difficult than previously anticipated.  

The Military Times article cited a new report by the Institute for the Study of War, which states: “The SDF has reportedly encountered intensified resistance and ‘better-emplaced defenses’ over the past four weeks following initial rapid gains in districts on the outskirts of [Raqqa].”

The OIR spokesperson acknowledged that SDF forces are “encountering tough ISIS resistance in Raqqa,” but claimed that the group is continuing to make progress every day. “Over the course of the last week, the SDF have cleared more than 35 [square kilometers] of ISIS-held territory, in and around Raqqa,” he added.

Citing security concerns, the Pentagon has remained reticent about the scope and nature of U.S. military involvement in the fight against ISIS since the start of the campaign. However, citizen journalists and local reporters have kept a steady stream of information about coalition activity in Syria flowing from the battlefield.

On July 18, the Turkish state news agency Anadolu published an article detailing  the extent of U.S. military operations in northern Syria. Not only did the article and accompanying map reveal the locations of U.S. bases  and outposts in the region, but also the types and number of personnel, weapons, and vehicles stationed at specific points.

The Pentagon appears shaken by the Anadolu report. “While we cannot independently verify the sources that contributed to this story,” it said in a statement to the Ankara-based international news agency, “we would be very concerned if officials from a NATO ally would purposefully endanger our forces by releasing sensitive information.”  

Turkey, a key NATO ally, appears to be closely monitoring the movement of U.S.-made weapons, equipment, and vehicles bound for the SDF, as the YPG fighters within its ranks are considered terrorists by Ankara. Turkey considers the YPG an extension of the Kurdish PKK, a separatist movement also designated a terrorist group by the United States and the European Union.

And this holds another possible use for those vehicles in the coming months. The uptick in cross-border skirmishes between Turkish government troops and YPG militants caused the U.S. to dispatch a contingent of special operations troops to the border last month to intervene — and, as Military Times notes, M-ATVs and MRAPs have been commonly used by U.S. special operations troops in Syria.

With special operations forces increasingly on the front lines of the War on Terror, that up-armored convoy may signal that the Pentagon’s elite troops are digging in for the long haul — to help keep the peace after Raqqa falls.