Russian military support crew members attach a satellite guided bomb to SU-34 jet fighter at Hmeimim airbase in Syria on Saturday. (Alexander Kots/Associated Press)

Donald Trump says: “Let [Russia] get rid of ISIS. What the hell do we care?” It is a fair question. What harm could come from letting Russian President Vladi­mir Putin take on this fight for us in Syria?

The answer is: plenty.

First, Russia is not fighting the Islamic State. According to the Institute for the Study of War, the Russian strikes have been mainly in areas controlled by other Sunni groups that Syrian President Bashar al-Assad sees as a threat, including rebel groups trained by and aligned with the United States. That is because Russia’s strategic goal is not to destroy the Islamic State, but to prop up the Iran-backed Assad regime — and to force the West to back him as well. By destroying the moderate opposition, the world will be left with a choice between Assad and the Islamic State. President Obama does not seem to understand this. Last week, he naively declared that Russia should not be targeting the U.S.-backed rebels because we need a moderate opposition to have a transition from Assad’s rule. That is precisely why Putin is targeting them.

Second, Russia’s intervention will actually strengthen the Islamic State. By eliminating moderate opposition, Russia is driving all Sunni groups into the arms of the Islamic State and the al-Qaeda-backed Jabhat al-Nusra — making them the only game in town for the majority of the population opposed to Assad, even if they do not share the terrorists’ radical ideology. This will radicalize the conflict and make Syria into an even greater magnet for jihadists. That helps Assad, who needs the Islamic State threat to justify his regime’s continued existence as a bulwark against them.

Third, Russia’s new presence in Syria strengthens Iran. It is no coincidence that Russia moved its forces into Syria just weeks after Iranian Quds Force commander Qasem Soleimani visited Moscow. Iran, the Shia face of Islamic radicalism, is on the march across the Middle East, and Russia’s intervention bolsters Iran’s quest for regional dominance. Both sides benefit. Russia gains a permanent foothold in the Middle East, with a major airbase and a warm-water port in the Mediterranean from which to project power and challenge the United States and our allies. Iran gets weapons (such as the advanced S-300 surface-to-air missile system to protect against a military strike on its nuclear program), and a new coalition to counter U.S. influence made up of Russia, Iran, Iraq, Syria and Lebanese Hezbollah. This is a disaster for U.S. interests. As retired Gen. Jack Keane put it on “Fox News Sunday,” a “Russian-Iranian alliance strategically is a game-changer for the Middle East. It is going to impact every country in the Middle East and likely diminish U.S. influence.”

Fourth, Russia’s intervention sends a dangerous message of American weakness. Obama declared war on the Islamic State and promised to “destroy” the terrorist network. The pretense of Russia’s intervention is that we are losing that fight and that Russia is coming to the rescue. It was our anemic military campaign (75 percent of U.S. air sorties do not drop any bombs) that created the vacuum that Russia is now filling.

Our weakness in Syria may have consequences beyond the region. It was Obama’s failure to enforce his red line on Assad’s use of chemical weapons that emboldened Putin to annex Crimea. With even more evidence of American weakness, Putin could further test U.S. resolve to defend our NATO allies in the Baltic states or others to which we have treaty obligations. He now has an airbase that puts Russian fighter jets five minutes from Turkey, a NATO ally. Other U.S. adversaries, such as China and North Korea, could also be emboldened to test our resolve. Weakness is provocative.

Fifth, Russia’s bombing campaign signals that the United States is an unreliable ally. When Russia warns the United States to “get out of the way” while it strikes forces we recruited and trained in the fight against the Islamic State, and we acquiesce, others depending on U.S. security guarantees lose confidence in us. The Iraqi government just reached an intelligence-sharing agreement with Iran and Russia. And Iraq’s prime minister said this weekend Russia is welcome to launch strikes against the Islamic State on its territory. Already we are talking with Russia about “de-conflicting” our air operations, which is a form of military cooperation. Supporting or tolerating Russian activities strengthens the growing belief in the region that we are allied with Russia, Iran, Assad, Hezbollah and Iraq’s Shia militias against all of our traditional allies.

Obama says we should not worry about any of this. Putin is acting out of “weakness,” he insists, and is getting himself into a “quagmire” much like the Soviet invasion of Afghanistan in 1979. Even if that were true, it should provide us with little comfort. What happened when the Soviets finally withdrew from Afghanistan? The Taliban took power and invited in al-Qaeda, which turned the country into a safe haven to plan the attacks of Sept. 11, 2001.

In other words, the Russian intervention in Syria is a geostrategic disaster for the United States.

That’s why the hell we care.

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