Russia is likely to bomb U.S. ground forces in Syria in the coming weeks.

It's a realistic assessment, not alarmism.

As Jamie McIntyre reported on Wednesday, two U.S. Air Force F-22 fighter jets intercepted and fired flares at two Russian Air Force SU-25 jets that had crossed east of the Euphrates river. CNN suggests a Russian SU-35 might also have been involved in the encounter.

While Wednesday's aerial encounter was not as serious as it might seem — utilizing their greater stand-off capabilities, the F-22s would have kept their distance if they anticipated having to engage Russian jets -- it's clear that tensions between the U.S. and Russia are building rapidly in Syria.

But when it comes to Russia's growing threat to U.S. ground forces, I have three specific concerns.

First, there's the context of escalating physical risk. As I noted in June and September, Russia has repeatedly threatened to attack U.S. personnel on the ground and in the air above Syria. Russian jets are also increasingly entered into U.S. controlled "deconfliction zones" east of the Euphrates river. That they are not responding to radio warnings (if they were, the F-22s wouldn't have fired flares) suggests that Russian aircrews have been instructed to challenge U.S.-controlled airspace. Because of the political sensitivities and the risks of miscalculation involved in such encounters, Russian commanders are almost certainly operating under orders from Russian President Vladimir Putin.

That speaks to the second concern, here: Putin's strategic calculus in Syria.

Put simply, the Russian leader wants the U.S. out of Syria in order to advance his interests and those of his partners. Putin knows that while the U.S. retains a military presence in eastern and northern Syria, the Russians, Iranians, Turks, and Assad won't be able to turn Syria into an artery of imperialism and sectarian terrorism.

Fortunately, Secretary of Defense James Mattis recognizes the reciprocal utility of a continued U.S. presence and President Trump seems to support him.

Still, if Putin believes that killing a few Americans with an "accidental" air strike would not meet retaliation and would help push the U.S. out of Syria, he'll do just that.

But that's only half of the strategic context. As I've explained, Putin's Middle Eastern actions are designed to displace the U.S. as the regional kingmaker and access lucrative feudal-mercantilist relationships with states like Saudi Arabia and Egypt. In that sense, Putin doesn't view U.S. interactions in Syria in a one-dimensional sense, but rather in the context of a regional political environment shaped by raw perceptions of power. The ensuing risk here is that Putin might believe killing U.S. military personnel in Syria would foster his regional perception as the international leader to deal with/kneel to.

Finally, there's Putin's strategic calculus with regards to President Trump.

Because if Putin believes that he can take aggressive action against U.S. interests without significant pushback from Trump, he will do so. And unfortunately, President Trump remains too willing to turn a blind eye to the KGB colonel's agenda. That explains where we are now: in a situation in which Russia believes it can continue to escalate without serious American riposte.

Yes, this time the Russian jets left the deconfliction zone. But what about the next time? What happens if Russian aircrews are ordered to ignore U.S. flares?

Trump must step up to the plate.

To protect those under his command and U.S. national security interests, Trump should issue an unequivocal warning to his Russian opposite. He should state that he has authorized U.S. aircrews to radar lock-on and if necessary, engage, any Russian jets that threaten U.S. forces in Syria. Whatever ongoing debates over U.S. policy towards Assad, Putin must be kept on a tight, deterrent leash.

American lives depend on it.