The United Nations Mission in South Sudan, or Unmiss, has been credited for sheltering vulnerable civilians on a scale never done before, though not for figuring out how to stop the fighting. Government forces and their rivals continue to battle over important oil regions. Peace talks are going nowhere. Peacekeepers can do little more than guard the civilians taking refuge in their bases — around 65,000 people. Fighting near one base in Malakal killed a 14-year-old child sheltering inside and wounded an unspecified number, the United Nations said Wednesday. Before that, civilians hunkering inside were wounded by stray bullets when the town last changed hands between rival factions.

And so what was once supposed to be a model United Nations exercise in a hopeful new nation, with a relatively small contingent of 7,000 peacekeepers and close cooperation with the country’s leaders, has turned into a defining crisis for the United Nations. The light footprint has not worked. Efforts to reinforce the mission have been bogged down. And the peacekeepers now find themselves with a tough mission of protecting civilians with no end to the fighting in sight.

The gravest risk for the United Nations now is the prospect of South Sudan’s conflict turning regional like the one in the Democratic Republic of Congo next door, which has over the years drawn an array of African countries into proxy battles for control of the country’s rich mineral resources. South Sudan has oil to fight over. Ugandan troops are already in the country, and on Wednesday their president, Yoweri Museveni, declared that Ugandan soldiers were fighting alongside troops loyal to the South Sudanese president, Salva Kiir.

“Unmiss deserves credit for defending so many civilians, but it has looked politically irrelevant as the war has intensified,” said Richard Gowan, an analyst at New York University. “In essence, Unmiss is now the custodian of tens of thousands of hostages. If there is no cease-fire or political settlement, every citizen who has fled to a U.N. base remains vulnerable to future violence.”

To restore its credibility, he said, the United Nations will need to step up its military and political investment in the country, which will not be easy. With a record 70,000-plus blue-helmeted troops in Africa today, committing more peacekeepers and a stronger mandate will certainly face difficulties on the Security Council.