Back in January, then-Secretary of State Rex Tillerson said that American objectives in Syria were to suppress any Islamic State (IS) resurgence, oust Bashar al-Assad from power, reduce Iranian influence, continue to back a Kurdish-dominated enclave and reassure our Turkish allies. This speech has now disappeared from the State Department website, along with all the former secretary of state's other pronouncements. And this week, President Donald Trump announced that American forces will soon be withdrawn from Syria, while the State Department put a hold on further stabilization assistance to areas liberated from IS.

Tillerson’s announced objectives were mutually incompatible and largely unachievable, even were the United States to sustain its modest level of military and economic engagement in Syria. Trump’s announcement, therefore, makes some sense, but only if conditioned on a more modest set of conditions for withdrawal.

The absolute minimum condition compatible with America’s honor and credibility is to help its Kurdish allies negotiate an arrangement with the Damascus regime (and with Turkey) that affords them some degree of political autonomy and allows them to continue to secure their population in the east of the country. Simply walking away and allowing these former partners to be crushed between two hostile forces would be the worst debacle for America since the fall of South Vietnam. What future partner would want to risk blood to support shared interests if their fate is to be discarded as soon as convenient?

The second condition for leaving would significantly improve the chances of not having to return. The United States could offer to fully withdraw its forces from Syria and normalize relations with the government in Damascus once all foreign militias have also left the country. Assad has won the civil war. If he wants to keep Russian and Iranian advisers, there is little to stop him. But Hezbollah fighters should return to Lebanon, and the thousands of other Shiite militias should return to Afghanistan and the other lands from whence they came. If they do not and instead they remain and bring their families, the ethnic makeup of the country will be permanently altered and Israel will permanently face an Iranian proxy on a second front.