Fast forward four years and the United Nations is struggling to alleviate the suffering inside its newest member. Last month, David Cameron announced that up to 300 British soldiers would join the UN peacekeeping force in South Sudan.

What lies in store for these troops is the task of dealing with the consequences of a new war that broke out in December 2013 – and is already largely forgotten by the outside world.

In a time of refugee crises, the British contingent will find that South Sudan has one of the biggest concentrations of fugitives in the world. No fewer than 2.2 million of the country’s people have been driven from their homes: 600,000 have fled to neighbouring states and another 1.6 million are “internally displaced” within their homeland.

Unity State has suffered more than anywhere else: in this verdant expanse of bush and wetland, some 580,000 people have abandoned their villages – between 70 and 80 per cent of the area's population.

The British soldiers will also discover that South Sudan’s civil war is just as futile as any conflict in the Middle East. Six ceasefire agreements and one final peace deal have come and gone without quelling the conflagration.

Instead, President Salva Kiir remains locked in a struggle for supremacy with Riek Machar, a former vice-president who was sacked in 2013. Rather than accept his dismissal, Mr Machar formed a rebel army and launched a revolt against Mr Kiir’s government.

Behind this clash between two power-hungry men lies the enmity of their respective ethnic groups – the Nuers of Mr Machar and the Dinkas of Mr Kiir. What began as a political battle has escalated into an ethnic war between the two largest tribes in South Sudan.

The suffering in Unity State is particularly intense because the local Nuer population is split between supporters of the government and the rebels. Mr Kiir managed to recapture large areas of this state by arming militias from a particular clan – the Bul Nuers – and turning them on other Nuers.

When the rebels attacked near Wangkei, it was Bul Nuer war parties – not the army – which set off in pursuit.

This fratricidal violence has inflicted immense suffering. Nyaful Kuma does not know her age, but she looks about 40. In June, gunmen raided the village of this mother of seven.

“I was at home when it started – I heard gunshots and I saw people who were killed,” she remembered.

As she took cover in her thatched hut, along with her terrified family, Mrs Kuma saw men with blazing torches setting fire to one home after another.

^{Nyaful Kuma and her son, Koang. Four of her children have been missing since gunmen raided her village and murdered her husband (DAVID BLAIR - TELEGRAPH)}

Her husband, Nyeway, summoned the courage to go outside to confront the attackers. “When the people came who were burning houses, he ran out to say ‘why are you doing this, why’?” said Mrs Kuma.

She saw what happened next. “They killed him with a gun,” she said simply.

After witnessing the murder of her husband, Mrs Kuma decided to gather her children and flee. As they ran, she caught a glimpse of her own hut going up in flames.

In the panic that followed, her children scattered in all directions. Today, Mrs Kuma has found refuge in the town of Mankien with two of her sons, Koang and Awiny, and one daughter, Nyathana.

Her other four children have been missing since the day her village was attacked. Mrs Kuma recited the names of her lost sons: Mariel, Chirangai and Chigai – and of her missing daughter, Nyadiet.

“We get no help here,” she added. “Nothing has come.”

This remote area lies beyond the reach of most emergency aid. No food distributions have taken place in Mankien, leaving people desperate enough to eat water lilies plucked from marshes.

The only aid agency operating here is Care International, which has helped restore local clinics and supply them with drugs. Care has also carried out a nutrition survey establishing the scale of hunger among local people.

This found that 21 per cent of children under five in Mayom County, which includes Mankien, were either moderately or severely malnourished. About seven per cent fell into the latter category, only one step away from outright starvation.

This should be harvest time – and the landscape has turned a vivid green under the annual rains. But the war has driven so many people from their homes that hardly any crops have been planted, so there is precious little to reap.

Thembisani Maphosa, the nutrition manager for Care International, described the situation as “alarming”, adding: “What makes it even worse is that people here have the land – they have the space – but there’s almost no farming going on.”

The result is that women and children wade through marshes in search of water lilies, which are then dried, crushed and cooked. When these meagre weeds have run out, desperate refugees must go elsewhere.

Nyakuah Koang’s village was destroyed by fighting in June. Along with her family, she found safety in the town of Riak. They lived on water lilies, which soon became impossible to find.

So the Koang family had to move again. Along with her mother and three sisters – none of whom knew their ages – Miss Koang wrapped her belongings in a bundle and set out for the town of Mayom.

After three days of walking, they were still about ten miles from their destination. “There was no food in Riak. No food. That is why we are moving,” said Miss Koang.

^{Nyakur Yieh, who was driven from her home in South Sudan, holds a water lily - the staple diet for refugees in remote areas beyond the reach of food aid (DAVID BLAIR - TELEGRAPH)}

The war deprives some of food – and others of the simplest life-saving precautions. No systematic vaccinations have taken place in Mayom County since soldiers looted the local clinics in 2014. Tens of thousands of children have gone without standard inoculations against polio, measles, diphtheria and tetanus.

The one crumb of good news is that Care International has helped to reopen the clinics and equip them with the refrigerators that allow vaccines to be stored.

But, as more war parties set off to hunt down rival marauders, South Sudan’s burden of suffering crushes ever more lives.