Could just be an overhyped coincidence but Putin has been known to engage in petty provocations of U.S. ships since Trump took office. He may feel he has no choice but to rattle his saber after last night. By attacking, Trump defied Russia’s umbrella of protection over Assad. If Putin doesn’t respond somehow, even if it’s nothing more than making a show of parking a Russian ship near the two American destroyers, he risks looking weak in his first big test of wills with Trump. A strongman can’t make a habit of tolerating defiance, especially so soon after protests swept his country.

A Russian warship entered the eastern Mediterranean Friday and was heading toward the area where two U.S. Navy destroyers launched missile strikes into Syria, Fox News has learned. The Russian frigate, Admiral Grigorovich RFS-494, crossed through the Bosphorus Strait “a few hours ago” from the Black Sea, according to a U.S. defense official… The frigate was bound for the Syrian port of Tartus on a routine voyage, the Russian news agency TASS reported Friday, citing a military-diplomatic source. “The Russian ship armed with cruise missiles Kalibr will visit the logistics base in Tartus, Syria,” the source said.

Maybe that’s true, or maybe it’s a pretext to sail past the American ships and signal that Russia’s patience with bombing Assad isn’t limitless. Meanwhile, back at the Pentagon:

Senior military officials say the U.S. is looking into whether Russia participated in Syria’s chemical weapons attack earlier this week. The officials say Russia has failed to control the Syrian government’s use of chemical weapons. They say a drone belonging either to Russia or Syria was seen hovering over the site of the chemical weapons attack Tuesday after it happened. The drone returned late in the day as citizens were going to a nearby hospital for treatment. Shortly afterward, officials say the hospital was bombed. The officials say they believe the hospital attack may have been an effort to cover up evidence of the attack.

Uh, what’s the next move if the investigation concludes that Russia did participate? The fact that Russians used to be stationed at that airfield makes it hard to believe they didn’t know chemical weapons were stashed there, but knowing about it and participating in the attack are two different things. I assume this is a leverage play by the White House aimed at Putin, i.e. “as long as you don’t retaliate against our airstrikes, we’ll make sure our investigation finds you innocent.” If Putin does retaliate somehow, then presumably America’s next move would be to pronounce Russia guilty of complicity in using WMD and try to organize new sanctions against them with Europe. But Putin likely won’t retaliate. As one Russian analyst told the Times, “There will be many screams on the Russian television with people condemning the strikes, but everybody understands that this is just a symbolic act meant for Trump to look different from Obama.”

Actually, the real point of the U.S. investigation is probably to warn Putin to prevent Assad from repeating his use of chemical weapons. If Russia is already publicly under suspicion for “letting” Assad use WMD, every further use going forward will deepen the suspicion. Trump isn’t worried about Moscow escalating, in all probability, but he may be worried about Assad escalating with another sarin attack, purely in the interest of showing his own supporters how willing he is to defy the U.S. And if that happens, Trump will be forced to attack again. The Pentagon investigation may be our way of nudging Russia to avert that scenario by placing some of their own credibility on the line if a new attack occurs. I can’t imagine Putin would want Assad to use WMDs knowing that it’s a de facto invitation for U.S. intervention of exactly this sort. The more he sticks to conventional types of slaughter — barrel bombs, chlorine, etc — the more we’re happy to leave Putin and Iran alone in their sandbox.

By the way, the AP is reporting that Syria appears to have had advance notice of the attack on the airfield last night, but that’s no surprise. Even if they didn’t evacuate as a precaution once they saw reports that the U.S. might attack (the airfield was a natural target since that’s where the chemical attack in Idlib originated), the Pentagon reportedly warned Russia 60-90 minutes before the tomahawks were fired that the airfield was in the crosshairs. Presumably the Russians passed that information along to Assad. If they didn’t, Putin and Assad are going to have an awkward conversation today.