THE first stretch of road seen by new UN troops in Congo after their arrival at the airport in Goma, the country’s second-biggest city, is a stark indicator of what lies ahead. The road—a rare bit of tarmac—was the site of a stunning victory not long ago by Tutsi fighters opposed to central rule. Heavily armed, they swept down from volcanic hills late last year to the shallow shores of Lake Kivu along the road to Sake, a smaller town where UN troops will soon be based, pushing demoralised Congolese government soldiers ahead of them (see map). Man-high grass on both sides of the road was for days littered with uniformed corpses, flies swarming over the slow, the drunk and the unlucky.

A 20,000-strong UN peacekeeping mission that has been in place since 1999 stood by and watched the rebels take Goma and hold it for several days. The UN Security Council, seeing its blue helmets humiliated, decided in March to send reinforcements of an unusual kind. The new troops are meant to “carry out targeted offensive operations…in a robust, highly mobile and versatile manner…with the responsibility of neutralising armed groups”. In other words, they are to fight a modern counter-insurgency campaign, a task the UN has never undertaken before. But will the troops really take the fight to the rebels? Or will they continue limp-wristedly to pretend to keep a peace that hasn’t existed for years? At stake is the possible end, or the continuation, of a conflict in which several million Africans have died.

The new UN intervention force comprises 3,000 soldiers from South Africa, Tanzania and Malawi, equipped with helicopters and armoured vehicles. The first units arrived on May 11th and the rest are expected in a month or two. They are led by a Tanzanian general who takes orders from the UN. At his disposal he will have infantry, artillery, special forces and reconnaissance teams.

Their arrival has been delayed—only a quarter of the troops are in place so far—by logistical glitches and bureaucratic wrangling. Goma airport, the main supply hub, is chaotic and vulnerable to rebel attacks. South Africa is said to be upset over not getting the command. Finding the right equipment has also been tricky. South Africa’s armed forces complain bitterly of being underfunded and overstretched. The government in Pretoria is keen to exert more influence in the rest of Africa, both politically and commercially, not least to match the United States and China. To bolster its claim, South African forces have trained specifically for Congo. In their country’s northern province of Limpopo they recently staged a mock battle involving gunships against a pretend rebel army hiding in the bush. Hawker jets flew bombing runs. “We prepare for every eventuality,” said an army spokesman.

But the enemy will be no pushover. The March 23rd Movement (M23), named after the date of an abortive peace accord the rebels signed with Congo’s government in 2009, has forced more than half a million people to flee their homes. The group was founded by about 2,000 soldiers from the national army who mutinied over poor pay and conditions a year ago. Previously they had been members of another rebel group, the National Congress for the Defence of the People, before it was officially integrated into Congo’s army. A report issued by the UN Security Council accused neighbouring Rwanda and Uganda of backing M23; both countries deny it.

The M23 is the largest of some 30 armed groups lurking near Lake Kivu. They harass the population, rape and kill with impunity, extort from small-scale miners, recruit child soldiers and do the bidding of commercial interests. “In total I have taken more than 40 women,” boasts one.

Congolese government troops who have been fighting the rebels are no more gentlemanly. Last November, after being routed from Goma and Sake, they streamed into the surrounding countryside and sowed mayhem. One bunch raped over 100 women in two days, including 33 girls, some as young as six. According to a UN report, they “entered houses, usually in groups of three to six and, after threatening the inhabitants, looted whatever they could find. One or two of the soldiers would leave with the looted goods and at least one would stand guard as the remaining soldiers raped women and girls in the house.”

These are the UN’s allies. The soldiers of the Congolese 391st battalion had been trained in 2010 by American mentors who at the time called them “a model for future reforms within the Congolese armed forces”. They were supposed to have imbibed lessons in human rights and warnings against rape. So the UN will have to do more than just go after rebels. Proper law-enforcement agencies will be needed.

But first it must deal with the insurgents. Vicious guerrilla fighting may lie ahead, a real test for the UN force. South African troops recently lost 13 men in the Central African Republic during a coup they were meant to prevent. In Congo, they will have to act in concert with two other armies, sharing unfamiliar equipment and tactics.

The rebels hope to exploit this. General Sultani Makenga, M23’s main military leader, observed the UN deployment from a grassy hillside above Goma. He appeared unruffled, pointing out how easy it would be for his machinegun-toting men to take over once again the road from the airport to the UN base. “They are on our land,” he says.

But M23 has become weaker in recent months. Bosco Ntaganda, a rival of General Makenga, was hounded out of the country in a power struggle and voluntarily gave himself up to the International Criminal Court at The Hague, which accuses him of crimes against humanity. Since then, hundreds of rebels have laid down their arms. Villagers report finding arrows, machetes and blades left behind by men who terrorised them not long ago. David Lusenge, now dressed as a civilian, deserted in April. “I have finally realised that I must serve my country in the regular army, and not in the bush,” he explains. Rebel leaders try to stop such desertions. Loyal M23 troops camped close to a UN base in Kiwanja, north-east of Goma, shoot at old comrades trying to sneak in.