The United States is in Syria mainly because of ISIS. At a recent event in Washington, the U.S. envoy to the anti-ISIS coalition Brett McGurk spelled this out: “We are in Syria to fight ISIS. That is our mission and our mission isn’t over, and we’re going to complete that mission.” More recently, Secretary of Defense James Mattis told Congress that the United States was not there to take sides in the broader civil war.

But it is also pursuing other interests there—including containing Iran’s influence, and also punishing the use of chemical weapons. “The United States has ... pursued [its interests] with different importance in different emphasis at different times,” Phillips said. “And that’s one of the reasons why U.S. policy has been largely unsuccessful.”

Prior to the rise of ISIS in 2014, the United States generally sought to contain the conflict, as efforts at international diplomacy failed to resolve it. The Obama administration advocated for Assad to step aside, but was reluctant to send weapons or funds to the rebels opposing him, out of fear that they would fall into the hands of Islamists and radical jihadists among them. In 2012, Obama also famously set a “red line” regarding chemical weapons, saying that their use would change his calculus on U.S. strategy there. But when Assad used sarin gas on civilians in 2013, Obama opted, instead of using force, for an agreement with Russia to destroy Assad’s stockpiles of chemical weapons. The U.S. started bombing Syria for the first time a year later, hitting not regime targets but targets associated with ISIS. It has continued bombing ever since.

President Trump recently said the U.S. would leave Syria “very soon”—even as his military advisers were planning to send additional troops. By the time he spoke, the U.S. presence in the country had grown to some 2,000 troops; news reports say Trump wants them out within six months.

Then came the suspected chemical attack of last weekend, to which Trump retaliated with strikes against the regime, as he did to a similar attack last year. This means the United States has once again expanded its mission beyond counterterrorism.

Europe

European countries like France and Britain are also in Syria because of ISIS. These countries’ policies have hewed largely to those of the United States—including, for the first time on Friday, participating in retaliatory attacks against Assad’s alleged use of chemical weapons—though the difference is that Europe is also grappling with the refugee crisis Syria has produced. The crisis has altered political dynamics on the continent, helping fuel electoral successes for far-right parties that oppose immigration.

“To face these threats, what we need is to stabilize Syria, and to stabilize we need a credible political transition,” Gérard Araud, the French ambassador to Washington, said this week. “The goal of the West should be political engagement with Russia, Turkey, [and] Iran with a view of political transition.” Both France and the U.K. joined the U.S. military action against Assad’s latest alleged use of chemical weapons.