Things are getting dicey in the skies above Syria as Russia continues to pound U.S.-backed rebels who are fighting ISIS as the U.S. looks to counter.

On June 16, the two sides nearly came to blows, as the Daily Beast reports:

The incident began when at least two twin-engine Su-34 bombers, some of Moscow’s most advanced warplanes, struck what the Pentagon described as a “border garrison” housing around 200 U.S.-supported rebels in At Tanf on the Syrian side of the Syria-Jordan border.

The rebels had been “conducting counter-ISIL operations in the area,” the Pentagon stated on June 18, using an alternative acronym for ISIS.

The United States and its allies in Syria clearly did not expect the air strike. The rebels in At Tanf are party to a shaky ceasefire agreement between rebel forces and the regime of Syrian president Bashar Al Assad—and, by extension, the Russian military contingent backing Al Assad. The Los Angeles Times reported that Russian planes had not previously been active over At Tanf.

The Su-34s’ initial strike wounded, and perhaps killed, some of the rebels in At Tanf.

The U.S. Navy scrambled F/A-18 fighters to intercept the Russians, the Los Angeles Times reported. The Navy has deployed two aircraft carriers to the region for strikes on ISIS. As the F/A-18s approached the Su-34s, officials with U.S. Central Command—which oversees America’s wars in the Middle East and Afghanistan—used a special hotline to contact their Russian counterparts directing Russia’s own intervention in Syria.

Arriving over At Tanf, the American pilots apparently spoke directly to the Russian aviators. “Pilots CAN communicate with one another on a communications channel set up to avoid air accidents,” Central Command confirmed in a statement to The Daily Beast.

Washington and Moscow had established the hotline as part of a so-called Safety of Flight Memorandum of Understanding that the two governments signed in October specifically in order to avoid the kind of aerial confrontation that occurred over Syria last week.

With the American jets flying close enough to visually identify the Su-34s, the Russians departed the air space over At Tanf. Some time shortly thereafter, the F/A-18s ran low on fuel and left the area in order to link up with an aerial tanker. That’s when the Su-34s reportedly returned to At Tanf—and bombed the rebels again.

According to the Los Angeles Times, the second strike killed first-responders assisting survivors of the first bombing run.

It's not known what rules of engagement American pilots are operating under over Syria, but you have to think, given the consequences, that the fighters would be allowed to open fire only under direct orders from their superiors.  If our F-18s had caught the Russians bombing the rebels, would those orders have been given? 

The day after the attack, what the Daily Beast describes as an "extraordinary" conference call was convened at the Pentagon with senior U.S. military officials and their Russian counterparts.  We can assume that the U.S. expressed its displeasure at Russian bombing anti-ISIS rebels who were also part of the ceasefire arrangement.  What the Russians replied is anyone's guess.

The Russians seem determined to force a military victory in the civil war.  That can't be done until all rebels either are dead or give up.  Moscow doesn't care who is backing the rebels and whom they are fighting.  Russia will apparently risk war with the U.S. to achieve its strategic objectives.

And since the U.S. has no discernible strategic objectives, we are stuck with reacting to Russia's aggressive moves.  The danger of overreacting isn't far away.