If the target wasn’t meant for the northwest, it would likely be one of the three strategic arteries Iran needs to complete its land bridge from Tehran to the Mediterranean Sea because Assad is dependent on Iranian-backed forces on the ground. Of the three, Deir al-Zour would top the list.

To reach Deir al-Zour, one would want to take the Abu Kamal-Qa’im border crossing. The corridor runs to the southeast of Raqqa and the province remains largely in the hands of the Islamic State. It was also the target of Iran’s recent launch of ballistic missiles.

Assad’s forces are advancing in that direction from Palmyra to the south and from Aleppo to the north. Meanwhile, Iran plans to have the Hashd al-Shaabi or its Popular Mobilization Units—a group of Shia militias that are, ostensibly, part of the Iraqi government’s security forces—take the eastern border zones while using its forces deployed in Syria to push from the west.

To that end, one of the Iraqi Shia militias under Iran’s stewardship announced their recent deployment to the border crossing and southeast Syria. Iraqi militias backed by Iran already took the border town of Al-Ba’aj from ISIS and told The Guardian that they are exploring possible paths to create a supply line to Deir al-Zour that could bypass the Abu Kamal-Qa’im crossing.

It is less likely that Assad would use chemical weapons on Raqqa. That warzone is on the Euphrates River where the U.S.-backed Syrian Democratic Forces are currently engaged with ISIS. It also is a few miles from where the United States recently downed the Syrian SU-22 fighter jet and where independent reports indicate the United States is building a fifth forward operating military base near Tabqah.

A chemical-weapons attack in the south is also not as likely—even if the area is the most strategic of the three. The main highway connecting Baghdad to Damascus runs through the southeast along Syria’s border with Jordan and Iraq.

It also happens to be where the United States and allied forces set up shop with a military outpost just over a year ago. The Al-Tanf border crossing is also a deconfliction area that recently became a flashpoint, prompting the United States to down several Iranian drones in the past few weeks. With U.S.-aligned forces increasingly under attack, the U.S. military has moved a High Mobility Artillery Rocket System into the area from Jordan to dissuade Iranian-backed militias from targeting American troops.

A chemical-weapons attack near either Tanf or Raqqa would risk killing U.S. soldiers or those of other important U.S. allies. In such a scenario, one could envision fire and brimstone representing President Trump’s definition of “a heavy price” in response. Therefore, for strategic reasons that also bump up against what is rationally possible for the regime, the most likely targets Assad would consider are Idlib and Deir al-Zour.

But Wait, There’s More . . .

There are additional points worth noting based on recent events. The fact that recent reporting describes the Syrians mixing precursor chemicals at the Shayrat airfield indicates that those stockpiles have probably not been moved since April. That is noteworthy because in the wake of Trump’s retaliatory Tomahawk strike, Assad reportedly moved many of his aircraft to the airbase at Bassel al-Assad International Airport. Nearby is Russia’s sizable Khmeimim Air Base in Latakia close to its other expanding land and sea assets. This could indicate that Russia has no desire to either host Assad’s chemical weapons or have them at a Syrian base close by. In other words, there’s a limit to how far in street Putin is willing to let Assad play.

Russia and the United States likely do not want a much larger military conflict between themselves, least of all over Syria. This points to the reality that it is quite likely the two will need to negotiate and agree on some form of settlement to the Syria conflict at some point down the road. The question remains what will be their red lines? Here, the Trump administration appears to understand something the Obama administration forgot, namely, that it helps to have a strong military position on the ground when negotiating at the table.

Another important lesson is that the pro-regime escalations at all three strategic locations in the south and east are not isolated incidents but the opening salvo in the next phase of the Syrian conflict. In this round, Iran will play a deeper role and a widening of the conflict is inevitable. That comports with reality because whether or not the White House publicly admits it, the answer to the war in Syria evolved long ago beyond the question of the Islamic State and the future of Bashar al-Assad. Increasingly, it is becoming about Iran.

Despite the official public statements regarding the single-minded United States focus on ISIS in Syria, the conversation I had Tuesday with a senior White House official left little room for doubt that the United States was more than prepared and has considered such a contingency. “Think of it as strategic communications. The cruise-missile strike wasn’t just a kinetic slap on the wrist. It was a clear message that under the Trump administration, red lines mean something.” The impression I received is that Tehran should take notice.

Matthew RJ Brodsky is a senior Middle East analyst at Wikistrat and former director of policy at the Jewish Policy Center in Washington, DC. He can be followed on Twitter: @RJBrodsky.

Image: Smoke rises after airstrikes on a rebel-held part of the southern city of Deraa, Syria, June 15, 2017. REUTERS/Alaa Al-Faqir.