Following Thursday’s report that Russia had recently informed the US of planned military operations against terrorist groups on the Syria-Jordan border, a company of US Marines conducted a live-fire exercise in the same area. Officials say it was intended to be a “warning” to Russia.

The exercise took place near the US base at al-Tanf, at the corner of Syria’s border with Iraq and Jordan. Though the US no longer really has any rebel allies in the area, which was the initially point of the Tanf base, the US does regularly attack any pro-Syrian forces who get too close.

The proximity of Islamists, especially al-Qaeda-linked groups on the Jordan border, has pretty much been ignored by the US. The possibility that Russian and Syrian forces might take care of those groups has infuriated the US, and led to threats of force.

Centcom officials continue to talk up the idea that they “will not hesitate to use necessary and proportionate force” if Russian, Syrian, or other pro-Syrian groups get too close to the Tanf base.

In the past, US forces have attacked pro-government militias for getting near Tanf, and have also attacked and killed hundreds of Russian military contractors on one occasion, an incident followed up by US bragging.

Though Pentagon officials are presenting this as standard operating procedure, it is anything but, particularly since Syria never authorized US troops to be there in the first place. Attacks on Russian troops would be a much bigger deal, and not something casually passed off as “self defense.”