SOUTH SUDAN appears to teetering — again — at the edge of an abyss. Since a power struggle between President Salva Kiir and his former vice president Riek Machar plunged the young nation into civil war a year ago , 1.9 million people have been displaced, famine has been knocking at the door and the stability so necessary to build for the future has been carelessly discarded.

Now, violence threatens to escalate. The end of the rainy season traditionally leads to renewed fighting, and there are multiple indicators that the forces of Mr. Kiir and Mr. Machar are poised to go on the offensive. “We will settle this with war,” one rebel commander told the International Crisis Group, which reports that Mr. Kiir’s government has spent tens of millions of dollars, largely from oil revenues, on arms. The conflict is morphing in new and dangerous directions. An ethnic divide was always present between Mr. Kiir, a Dinka, and Mr. Machar, a Nuer, but now the seething hatreds are sinking deeper into fragmented militias.

According to the International Crisis Group, the Nuer White Armies have flourished and “are only tenuously controlled by their sponsors.” At least two dozen armed entities are now operating in South Sudan, the group reports, including the government and opposition. Entire ethnic communities are now at war with each other. All this roiling violence will be harder to stop. The two main protagonists, while attending peace talks, have shown little proclivity to settle. The hopeful moment of South Sudan’s independence in July 2011, after decades of civil war, now seems like a distant and lost dream.

Fresh violence will tip the nation into a deeper humanitarian crisis, already one of the worst on the planet. The International Rescue Committee reports that out of a total population of 12 million, some 1.4 million have been displaced by the violence inside the country and nearly a half million become refugees. Tens of thousands of people have died in the fighting, which has also been accompanied by widespread rape and use of child soldiers. An estimated 100,000 people are sheltering in U.N. peacekeeping camps, fearful of leaving for home lest they face renewed attacks.

Last spring, there were dire warnings of a famine, which was barely averted by international humanitarian relief efforts, but food needs are still acute and will be made worse if war flares anew. The United States has spent hundreds of millions of dollars attempting to alleviate the suffering; others have contributed as well. Secretary of State John Kerry warned President Kiir during a visit in May that events have reached a critical point and that if the fighting does not stop, Mr. Kiir and Mr. Machar will “completely destroy what they are fighting to inherit.”

From the United Nations, from South Sudan’s many international benefactors, from almost every quarter has come the same warning: The guns must be laid down to save South Sudan. Soon, the answer will be heard, and the rumblings are not encouraging.