The events on the border have already been declared a Level Three emergency - the highest on the Rohn scale of emergencies within the World Food Programme - akin to the disasters seen in Pakistan during the floods and the Haiti earthquake.

We saw two-year-old Alshadooz Suleiman, who had just arrived at the Yida camp, barely able to cry through weakness. She is suffering from severe malnutrition, too exhausted to even eat.

She and her mother and two other siblings trekked for six days to reach this camp. Here the medics from the charity Samaritan Pulse will care for her and she should live but nothing is certain in these brutal conditions where most people are just trying to survive from day to day.

The world's newest nation, South Sudan, which hasn't even celebrated a year of independence is now readying itself for battle. It is sending more and more of its troops to the frontline to repel what it believes will be further attacks by the north into their territory.

The rhetoric between the two governments shows no sign of letting up either with the Khartoum government in the north declaring a state of emergency in the states along the border.

It is unlikely to make a difference to the civilians who are caught up in the unrest. Thousands of them are fleeing from the Nuba mountains on the border where they have been living in caves out of fear of the aerial bombing attacks being carried out by the north.

In Yida refugee camp, alongside Alshadooz, we found at least 20,000 people who had fled the unrest - amongst them many other children in a severe state of malnutrition.

The families had travelled almost a week through mountainous terrain to reach the relative safety of the camp. Once in Yida they are given food, water and medicines.

Around 200 to 300 have been arriving every day - on one day alone, around 600 people turned up asking for help.

"These people are hardy people," the World Food Programme's Geoffrey Pinnick told Sky News.

"They would not leave their homes in the Nuba mountains if there was any other way. But they tell us they have been reduced to eating berries and seeds."

Sudan fought a brutal civil war for decades which claimed two million lives and displaced up to five million civilians. Independence for South Sudan in July 2011 was meant to herald a new beginning for both countries.

But over the past few weeks, the military in the south - the Sudanese People's Liberation Movement (SPLM) army - has beaten back several assaults by the northern army.

During one such incursion, the SPLM army seized the critical oil hub of Heglig which lies in an area both countries are contesting.

But the southern troops withdrew after pressure from the United Nations as well as others, including the UK and the European Union.

Now South Sudan very much feels like it is fighting for its survival, especially given the aim of the government in the north appears to be seize oil fields and territory without agreement or negotiation.

When we joined South Sudanese troops on the frontline we found high morale and a determination to fight for what they believe is theirs.

Major General James Gaduel, division commander, told me: "Now is the time to arrest (Sudan President) Omar Bashir and if the international community won't do it, then we will."

The South believes President Bashir is responsible for a host of human rights abuses and they have been backed up by the International Criminal Court which has indicted him for war crimes.

Certainly in Bentiu state hospital, the beds are filled with civilians who have been maimed or scarred by bombs dropped on the orders of President Bashir.

Mohammed was working in his market stall in Bentiu - some 50 miles inside Southern Sudan territory when bombs started falling from the Russian-made Antonov cargo planes purchased by the north.

He was burnt over most of his body but should make a recovery.

In the next bed is Kereni Mayok, a 28-year-old footballer who was returning from training when the Antonovs began dropping bombs again.

And next to him is Mayel Ran, 7, who lost his right arm when a bomb landed on his house.

Independence wasn't meant to be like this. They hoped for a better future. Now it looks more uncertain than ever.