U.S. officials declared on Monday that they are convinced Russian warplanes were deliberately targeting CIA-backed Syrian rebels.

The Wall Street Journal reports that the grim assessment of intelligence officials and commanders on the ground has “deepened U.S. anger at Moscow and sparked a debate within the administration over how the U.S. can come to the aid of its proxy forces without getting sucked deeper into a proxy war that President Barack Obama says he doesn’t want.”

Putin has, in the past week, taken unambiguous action to protect Syrian president Bashar Assad and roll up the American-backed elements of the Syrian rebellion, leaving the American president with no option but acceptance of the Russian agenda. In fact, Putin will arrange Obama’s complicity in his agenda by taking out every threat to Assad that Western powers could have supported, and then demanding they finish the job of securing the Syrian regime by taking out ISIS, as President Obama has talked about doing ever since he was forced to start paying attention to the “junior varsity team” of terrorism.

Administration officials declared Obama “neither wants a proxy war with Russia nor to let Moscow distract the U.S. from its fight against Islamic State,” while the Pentagon spoke of protecting units it has tasked with fighting ISIS exclusively — the very units Putin would be least interested in bombing.

The most obvious way to defend the units Putin is bombing, without air-to-air battles between American and Russian fighters, would be issuing effective surface-to-air missiles to rebel forces, but that is a non-starter due to entirely reasonable fears about such weapons falling into the hands of terrorists, who could turn them against commercial airliners. Expect the Russians to make coy references to that ugly possibility when they note how President Obama’s lack of faith in his own proxy fighters reinforces the Russian-Iranian-Syrian narrative that they are all terrorists who never offered a legitimate challenge to Assad’s rule.

According to the Wall Street Journal article, U.S. officials described Russia’s targeting of American allies as a “direct challenge to Mr. Obama’s Syria policy.” The Pentagon stopped sharing information about its proxy forces in Syria with the Russians because it “suspected Russia would use that information to target them more directly or provide the information to President Bashar al-Assad’s regime.”

One senior American official talked about how it was possible to wave off a few bombs dropping on American allies as a mistake, but “on day three and day four, there’s no question it’s intentional. They know what they’re hitting.”

Members of the targeted Syrian units understand Putin’s checkmate strategy better than anyone in the Obama Administration. According to the Journal, rebel fighters said in interviews, “They believed they were being targeted by the Russians to weaken the moderates, without whom the West would have to accept Mr. Assad’s continued rule,” because the remaining rebel groups are “too radical for the West to work with.”

One rebel officer said he spoke with “coalition officials” after getting bombed by the Russians, and they “offered condolences but little in the way of concrete support.” Another said he was given “nothing specific” when he asked for help.

The Russians are now denying that they’re moving ground forces into Syria, but allowing that Russian “volunteers” might just pop up alongside Assad’s forces and the Iranians, the same way those “little green men” magically appeared in Ukraine. At one point, Moscow tried claiming that Russian troops fighting in Ukraine were merely enjoying themselves on vacation. It looks like a sizable number of Russian soldiers are considering vacations in Damascus this year.