Last week there seemed to be an apparent escalation in the ongoing civil war/genocide/ethnic cleansing that is the current state of affairs in Bashar Assad’s Syria.

With the demise of ISIS as a pseudo-national entity, the various opponents of ISIS are now jockeying for position. These include, but are not limited to, the Syrian regime forces which are aided by Russia; Iranian militias; Iranian proxies such as Lebanese Hezbollah (which we, inexplicably, equip via our “security” agreement with the Lebanese Army) and the Iranian owned and operated Iraqi Popular Mobilization Units, or PMUs (which we also, inexplicably, equip and possibly train via our “security” agreement with the Iraqi Army); the al-Qaeda-lite known as the al-Nusra Front; Syrian Kurds; the Turks; and our dog in the fight, the Syrian Democratic Forces (SDF). Complicating all of that, US policy in Syria is regime change. This means our proxy is in direct opposition to the war aims of most of the other parties.

It was reported that Syrian regime forces had launched a major attack on the SDF near Khusham. This particular piece of dirt is important because it establishes control over a major oil field.

In a major clash the U.S.-led military coalition in Syria has killed more than 100 troops allied with the regime of Bashar Assad — after some 500 soldiers backed by tanks launched what appeared to be a “coordinated attack” on a headquarters of rebel fighters being trained by American advisers, military officials revealed late Wednesday.

The combination of air and artillery strikes came after pro-regime troops attacked the compound of the Syrian Democratic Forces in Khusham, Syria, according to a military spokesman.

One SDF soldier was wounded, said Col. Thomas Veale of the Combined Joint Task Force Operation Inherent Resolve, the command that is directing the battle against the Islamic State terrorist group in Iraq and Syria.

The Syrian Democratic Forces have been a crucial American ally in the fight against ISIS.

“After 20 to 30 artillery and tank rounds landed within 500 meters of the SDF headquarters location, Syrian Democratic Forces supported by the Coalition targeted the aggressors with a combination of air and artillery strikes,” the statement said. “Coalition advisers were with the SDF in an advise, assist and accompany capacity, and this action was taken in self-defense.”

Now there is an unexpected twist on the story.

U.S. forces killed scores of Russian mercenaries in Syria last week in what may be the deadliest clash between citizens of the former foes since the Cold War, according to one U.S. official and three Russians familiar with the matter.

More than 200 contract soldiers, mostly Russians fighting on behalf of Syrian leader Bashar al-Assad, died in a failed attack on a base held by U.S. and mainly Kurdish forces in the oil-rich Deir Ezzor region, two of the Russians said. The U.S. official put the death toll at about 100, with 200 to 300 injured.

The other interesting parts of the puzzle.

The US and Russia had established a “deconfliction” line that was rivers. Rivers are not all that common in eastern Syria so the incursion was hardly accidental. And this:

The U.S., which has advisers stationed at the base alongside Syrian Democratic Forces troops, responded with aircraft and artillery fire.

“Coalition officials were in regular communication with Russian counterparts before, during and after the thwarted, unprovoked attack,” [Colonel Thomas F. Veale, a spokesman for the U.S. military], said . No fatalities were reported on the coalition side and “enemy vehicles and personnel who turned around and headed back west were not targeted.”

In the words of Defense Secretary James Mattis, this was “perplexing.”

Apparently, no one knows who is footing the bill for the Russian mercenaries, but I would suspect that some of that payment is from the nearly $2 billion in cash delivered by Obama to Tehran by airplane.

Was this a rogue operation dreamed up by a local commander? Hard to tell. The Russians aren’t known for initiative and contract troops aren’t known for taking risks (during the mercenary wars in Renaissance Italy, two famous mercenary companies fought all day and the sole fatality was a single man-at-arms who fell off his horse and drowned in a stream). So I vote against rogue operation.

The fact that the Russians were in contact with US forces at all times during the operation is interesting.

My guess is that this was an operation designed to grab a U.S. held base as a way of showing our proxies they couldn’t rely on us. The use of Russians was probably intentional and a way of daring us to use US firepower. In fact, the operation was probably based on the premise that we would allow the Russians to go head-to-head with the SDF and without interference.

Regardless, this was an expensive lesson. The Russian army is not much of an army when measured against the standard of any Western European army. In fact, it isn’t all that good anywhere if it can’t employ overwhelming force as it did in Georgia. One would expect this Russian Private Military Contractor to have some of the best manpower the Russians have turned out. Losing 300 of them at one sitting is not good for your business model. It is going to make recruiting much more difficult and it isn’t going help the PMC’s marketing effort.

It also laid down a marker. That the US will help the SDF and that message has to have been heard loud and clear in Tehran as well as in Moscow.