President Trump’s delegation of authority to Defense Secretary James Mattis has resulted in what looks like a quiet loosening of the rules of engagement with Iranian forces in the Iraq – Syria theater of operations.

According to Julian Borger of the UK’s Guardian, U.S. forces have opened fire on Iranian-backed forces in Syria at least three times since May. Three of the incidents took place at al-Tanf, a remote desert outpost near the point where the Syrian, Iraqi and Jordanian borders meet. There, a 150-strong force of US soldiers who are training local fighters to take on the Islamic State (Isis) was approached by convoys of militias fighting for the Assad regime. They responded with air strikes.

The encroaching forces seem to have been a mix of Syrian and Iraqi Shia militias, possibly accompanied by their chief sponsor, Iran’s Islamic revolutionary guard corps (IRGC) says Borger.

Borger says the IGRC was not concerned about hiding its fingerprints. The commander of its Quds force, Qassem Soleimani, had himself photographed with militia forces nearby and a drone shot down by US forces after it had dropped a bomb near them turned out to be Iranian-made.

There is an agreed upon 55-kilometer “deconfliction zone” around the al-Tanf region, however, Iranian-back militias have penetrated deep into the zone and militias aligned to Syrian President Bashar al-Assad and groups backed by Iran have steadily massed forces just outside deconfliction zone since the beginning of May. Those forces have tanks, artillery and modified pickup trucks with mounted heavy weapons, reports Shawn Snow of Military Times.

Force protection at the remote base has been a primary concern, according to officials at U.S. Central Command. The U.S. military has “ensured our forces are prepared and ready to defend themselves,” U.S. air-power has “constant coverage over our forces at al-Tanf,” to respond to hostile actors and to watch threats to U.S. and partner forces at the facility said Col. Ryan Dillon, a spokesperson for Operation Inherent Resolve.

On May 18, coalition jets launched a strike against a pro-regime convoy that had trespassed into the deconfliction zone after that convoy refused to react to a show-of-force flyover and warning shots. The airstrike destroyed an armored vehicle and bulldozer. Those forces halted their forward progress but are still deep within the zone, and are considered a threat, Dillon said according to reporting by Shawn Snow.

However, as reported above, forces outside the deconfliction zone are continuing to mass and are actively patrolling the area.

So why is al-Tanf so important?

U.S.-backed rebels took al-Tanf from the Islamic State last year, and it could be a launchpad to capture other territory on the Iraq – Syria border.

However, conservative analysts suspect that blocking Iranian-backed militias is also a key reason to hold al-Tanf.

The presence of the U.S. forces on the Syrian side near al-Tanf has prevented Iran-backed Shi’ite forces supporting Assad’s government from receiving supplies along the main Baghdad-Damascus highway.

The militias’ primary goal in intruding into the area is to establish a land corridor to link Iran with Damascus and its Shia proxy Hezbollah in Lebanon. “it is a key part of a network of connections for Iran," said Luke Coffey, director of the Douglas and Sarah Allison Center for Foreign Policy at The Heritage Foundation in Washington, D.C.

After the May and June incidents between US forces and the Iranian-backed militias the Pentagon on June 14 announced the deployment of the truck-mounted High Mobility Artillery Rocket System (HIMARS) to the al-Tanf base, so it looks like things are heating up.

“No doubt the local commander will have the proper rules of engagement to defend the base,” said the Heritage Foundation’s Luke Coffey. The Trump administration has provided more leeway to ground commanders to make tactical and strategic decisions, which will greatly aid the situation, a stark change in policy from the previous administration, Coffey said. “When the time is right, ground commanders will act.”