TOWNSHEND, Vt. — The civil war in Syria is over. Now it is time to stop the fighting.

Aided by Russia, Iran, Shiite militias and Hezbollah, the government of President Bashar al-Assad is on the verge of taking Aleppo, once Syria’s largest city. Supported by its powerful allies, the Syrian Army will then move to eliminate the remaining pockets of resistance, notably around the northern city of Idlib. While Iran has been Mr. Assad’s most important military ally, the Syrian regime would still want to have Russian airpower to finish its reconquest of the country’s populous west.

The Assad regime has prevailed through tactics of unspeakable brutality — barrel bombs, starvation, the targeting of hospitals and rescue workers and the suspected use of chemical weapons — but it has prevailed. Samantha Power, the United States ambassador to the United Nations, has rightly focused attention on these war crimes, but these denunciations will make no difference to the situation on the ground.

There is an absolutely counterproductive idea favored by Washington’s foreign policy elites of both parties, recycled recently by President Bill Clinton’s secretary of state Madeleine K. Albright and Stephen J. Hadley, national security adviser to President George W. Bush, for providing additional military support to the moderate Syrian opposition. Such aid cannot possibly now change the trajectory of the war, but will certainly get more people killed.

Though the outcome is clear, how the war ends matters greatly. The United States has an interest in a result that allows as many Syrians as possible to go home, that ensures the total defeat of the Islamic State and other extremist groups, and that safeguards the Syrian Kurds, who have been America’s principal ally against the Islamic State.