South Sudan, a new nation midwifed into being by the United States out of the ashes of war, is sinking into a mire of senseless violence and chaos. President Salva Kiir and rebel leader Riek Machar are wrecking their country in a conflict that has lasted more than 100 days and threatens more severe human suffering in the months ahead.

Since a schism between the two men triggered fighting between their forces in December, an estimated 1 million people have been driven from their homes.

International relief workers are warning that time is running out to avert widespread hunger.

The cause of all this misery is a bitter conflict between Kiir, from the majority Dinka ethnic group, and Machar, of the Nuer group. Their forces have continued fighting despite a January cease-fire agreement. The violence has impeded humanitarian work everywhere in the country. Diseases including measles, malaria, meningitis and diarrheal illnesses threaten the population.

It is not hard to put together a checklist of what should be done. First, Kiir and Machar must stand down their forces and participate in a democratic process that includes all. They must stop attacks on humanitarian aid workers and convoys so that desperately needed food and medicine can get through.

South Sudan’s independence was a foreign policy success for the Obama administration, but it is turning into a nightmare. The United States can still help the people of South Sudan build a better future, but first, and urgently, Kiir and Machar must step back from the abyss.