The MI-17 helicopter rocks and shudders into life, the rotors accelerating until flight UN863 is airborne and skimming the rooftops of Goma for another mission in the Democratic Republic of Congo.
The helicopter is Russian-made, the crew is Indian and the passengers comprise South African infantrymen, a Uruguayan officer, a Filipino technician and an American diplomat: classic UN peacekeeping.
The trouble is, the land below barely has a peace to keep. Thousands of Rwandan troops massed on the border this week and threatened to invade, prompting frenzied diplomatic efforts to avert a new war.
Amid the valleys and volcanic hills ringing Lake Kivu, and the corrugated tin cities and thatched villages bordering Rwanda, war is brewing.
The helicopter banks right over the town of Bweremana, host to hundreds of families who fled fighting in the mountains.
It swoops over the town of Minova, where drunk Mayi-Mayi militias control roadblocks and where the UN abandoned a base this year because of security fears.
Then the forests below, a blanket of green, from where reports and rumors seep of burnt settlements, atrocities and invasion.
Two years after peace accords supposedly paved the way for an end to Congo's agony, it was not supposed to be like this.
Foreign armies that backed opposing sides in the five-year civil war withdrew, rival Congolese factions formed an interim government in the capital Kinshasa, and the UN deployed its biggest, most expensive peacekeeping force.
In an impoverished land the size of western Europe, with a shattered infrastructure and numerous armed groups, nobody said forging peace would be easy. But it was hoped that a holocaust that had consumed more than 3 million lives -- the worst single-conflict death toll since 1945 -- was ending.
This week it threatened to reignite. At a closed-door briefing on Thursday, the head of UN peacekeeping, Jean-Marie Guehenno, reportedly told the security council that eight Rwandan battalions, massed on Congo's border, might invade and tip the Great Lakes region back into the abyss.
Aerial photographs and ground sightings suggested that Rwandan troops had already crossed the border. UN aid workers recorded claims of fierce fighting and looting from thousands of people fleeing through the forests.
"Atrocities are also taking place. We expect more displaced people in the coming days," said Bernard Leflaive, of the UN's office for the coordination of humanitarian affairs in Goma, a provincial capital bordering Rwanda.
Despite the accords, fighting never stopped. Instead of integrating into a new, unified army, militias and rebel groups continued sporadic clashes. But they tended to be local affairs, so-called micro-conflicts. The danger now is of an escalation back to full-scale regional war.
The crisis started last week when Rwanda's Tutsi-led government threatened to send in troops to search Congo's forests for Rwandan Hutu rebels, including those responsible for the 1994 genocide that killed 800,000 Tutsis and moderate Hutus.
President Paul Kagame of Rwanda told the UN and the African Union that a brief military action was planned.
While Friday, Kagame's adviser, Richard Sezibera, denied that troops had crossed the frontier, diplomats in the Rwandan capital Kigali said they believed that troops were in Congo -- possibly small units of special forces.