US forces destroyed the headquarters of their anti-ISIS efforts in Syria on Wednesday, The Wall Street Journal reports.

Turkish-backed Syrian forces advanced on the position, despite a US show of force, including F-15 fighters and Apache helicopters.

On Friday, Turkish forces fired at a US position in Syria, which some US officials say was deliberate.

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The US military destroyed its own anti-ISIS headquarters in Syria, The Wall Street Journal reported Wednesday, to prevent them from falling into the hands of fighters backed by Turkey.

According to WSJ, Turkish-backed troops advanced on the facility, which had been used to equip and train SDF fighters against ISIS, on Tuesday, leading US officials to quickly withdraw US troops and destroy the base on Wednesday.

As the Turkish-back fighters moved closer, US troops attempted to repel them, using F-15s and Apache helicopters as a show of force to warn them away while US troops were still there. But, according to The Wall Street Journal, the airpower failed to dissuade the Turkish-backed forces; SDF fighters fled and set fire to their part of the base, and US troops left before US assets destroyed the base.

Insider reached out to the US operation in Syria to request more information about what assets were used to destroy the base, but did not receive a response by press time. It is also unclear what was being held in the base, although The Wall Street Journal noted that it had previously been used to store light arms and ammunition for the SDF.

Last Friday, Turkish forces fired at an American position in Syria; while no casualties were sustained it came after reassurances from Chairman of the Joint Chiefs of Staff Gen. Mark Milley that Turkey knew where US troops were stationed. An officer familiar with the situation told The Washington Post that the incident was likely not accidental, as Turkish forces were aware of the US position, and had been for months.

"#Coalition forces continue a deliberate withdrawal from northeast #Syria. On Oct. 16, we vacated the Lafarge Cement Factory, Raqqa, and Tabqah," Col. Myles. B. Caggins, a spokesperson for the US-led coalition to defeat ISIS, tweeted Wednesday, referring to the base, the LaFarge Cement Factory, on which US forces carried out strikes.

Two F-15E Strike Eagles conducted an airstrike on the LaFarge factory to keep munitions and military equipment from the hands of the Turkish-backed armed groups, a coalition spokesman said.

Read more: Trump's sanctions against Turkey won't do anything to stop its invasion of Syria — and they might even add fuel to the fire

Vice President Mike Pence and Secretary of State Mike Pompeo are on their way to Ankara to try and broker a ceasefire. The two officials are set to meet with Erdogan on Thursday, according to The New York Times.

The US has already imposed sanctions on Turkey due to its incursion in what was Kurdish-controlled northeastern Syria, but pressing pause on a $100 billion trade deal between the two NATO allies and re-imposing a 50% tariff on Turkish steel exports has not deterred Erdogan. Pence and Pompeo, along with the State Department's special envoy for Syrian affairs James Jeffrey and National Security Adviser Robert O'Brien, are expected to threaten harsher sanctions should Erdogan refuse a ceasefire.