That did not stop the administration from pursuing quixotic and ultimately humiliating negotiations with the Russians throughout 2016. With the use of force off the table, we were forced to engage with the Russians over the fate of East Aleppo, in particular, as if the Russians were genuine partners for peace and not in fact enabling the very deliberate, brutal regime offensive that brought the last stronghold of the moderate opposition in Syria to its knees. We initially offered up carrots—such as increased military and intelligence cooperation with the Russians against Islamist extremists—if they would help us remove Bashar al-Assad from power, but by the end, we were practically begging the Russians to just let humanitarian aid shipments into East Aleppo. As one of the U.S. negotiators, I found the whole experience degrading.

Boy, that’s not the position Rex Tillerson is in now. Secretary Tillerson—who, I hear, has far less patience for the Russian foreign minister, Sergei Lavrov, than John Kerry did—can now walk into negotiations with everyone at the table understanding this president is willing to use force in a way his predecessor was not. It’s not quite time for Bashar al-Assad to go shopping for dachas in Sochi, but he might want to retain a real estate agent just in case.

The fight against the Islamic State just got harder. I had two big fears about striking the Assad regime. The first was that we might inadvertently kill some Russians. The Russian presence in Syria is much more robust than it was in 2013. The Trump administration mitigated that risk by loudly telegraphing its pass in a way that seems to have given the Russians plenty of advance warning.

My second fear was that this would greatly complicate the fight against the Islamic State. For the past two years, U.S. and coalition aircraft have flown in and around one of the world’s more robust air defense systems without the Syrian regime harassing the pilots. We had a few incidents where Russian jets got too close to U.S. aircraft or Syrian anti-aircraft radar lit up U.S. or coalition aircraft, but for the most part, the air war has gone forward unimpeded.

Both Russia and the Syrian regime, though, are still well-positioned to play the spoiler. They can affect the flights of U.S. aircraft in eastern Syria by activating their air defenses and have, in recent months, brought in more advanced air-defense weaponry that has even the Israelis nervous. They’ve also “accidentally” struck U.S.-backed rebel groups fighting the Islamic State.

How will the regime respond? I have no idea. Perhaps, now that they understand force is on the table, they will meekly accept what the United States has just done. Or they can begin to harass coalition pilots or more U.S.-allied rebels. Again, I don’t know. But I do know that America’s coalition partners in Syria and Iraq are all likely much more nervous about what this means for their own forces. Secretary Mattis is going to need to make some calls to soothe some jittery allies.