The man on the ground in the big blue hat stands under an unforgiving sun on the edge of an empty field in rebel-held territory near a town called Din Din, in South Sudan's famine-stricken Unity state. 

He reads a waybill number into his two-way radio: "Commodity, sorghum. One eight metric tonnes. Commodity, pulses. Two zero zero bags."

The radio crackles back to life with a "Roger" from the voice with a Russian accent on the other end. "Next call five minutes. Inbound for life run." 

The pilot of an Ilyushin aircraft makes a first pass overhead, part of a massive food drop organized by the UN's World Food Program in one of two declared famine zones in the central northern state.

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The blue sacks dropped from the plane contain a fortified cereal mix that helps stave off acute malnutrition in children under five. (Stephanie Jenzer/CBC)

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John Kimenia of Kenya is a veteran of World Food Program airdrops in Africa. He’s in contact with planes that fly from air hubs in Juba, South Sudan, and Entebbe, Uganda. (Stephanie Jenzer/CBC)

More than 400 metric tonnes will have fallen from the sky by the time they're done, with planes taking part from as far away as Entebbe, Uganda, to the south and Addis Ababa, Ethiopia, to the east.

The emergency food is expected to last at least a month for more than 20,000 people driven from their homes by the country's brutal civil war. The WFP has dropped here once before, 30 days ago.

From the ground, the sacks of grain look like packets of coloured candy tumbling through the air. They land with a thud, sending up great billowing puffs of dirt that give the horizon a scorched-earth effect.

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"The last one was not enough," said Sarah Nyakuonypuck, clutching ration cards for a group of 30 people.

"One card can't help a family."

The long lines are filled mostly with women. They wait for what they call "porters," who are hired by the aid agencies to drag the 50-kilogram bags off the field to sorting areas. There are also special bags containing nutrients for malnourished children.   

Most of the food is hauled by women whose husbands are either dead or fighting or simply not around.

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A woman carries a heavy bag of food following an airdrop near Din Din. (Stephanie Jenzer/CBC)

The 3½ years of civil war in South Sudan have displaced hundreds of thousands of people, especially in oil rich Unity state. 

Most of the people who have gathered for collective safety near Din Din were driven out of their villages late last year. They're civilians who say they're paying a terrible price for living in rebel-held territory.

Riek Machar, the leader of the rebel-faction Sudan People's Liberation Movement-In-Opposition, was born in the nearby town of Leer. Local leaders say that's why their people are being persecuted.

'They sleep when they're too hungry'

Aliza Nyakuma, 32, says her husband was shot dead when government soldiers attacked her village and burned it to the ground in January 2016. She hid in nearby swamps with her five children.

"They sleep when they're too hungry," she said of the children now. "And I go out and find the leaves of the trees. That's how my children survive. And eating water lilies."

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Aliza Nyakuma says her husband was killed last year by government soldiers. She has five kids, including two little girls who she says are sick with hunger. Sometimes, she ends up feeding them water lilies. (Stephanie Jenzer/CBC)

Nyakuma says she feels fear when she sees the planes overhead because she assumes they belong to "the enemy." She relaxes when the belly of the plane opens up to release the food parcels.

Airdrops have become a last resort and — in some cases — the only option for aid agencies like the World Food Program as they try to reach people trapped by fighting or who can't be reached on the ground. Vast tracts of South Sudan have very few serviceable roads.

Negotiating permissions from the government of President Salva Kiir in the southern capital of Juba to drop food in opposition territory is a big challenge and aid workers have become targets in a war taking on disturbing ethnic tones.

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South Sudan won its independence from Sudan in 2011 but quickly fell into civil war, with fighting breaking out in 2013.

The conflict has since fractured, increasingly along ethnic or tribal lines, pitting President Kiir's ethnic Dinka group against Machar's Nuer.

"Distribution of food cannot be on a regular basis due to the security situation," said Serge Tissot, the head of the UN's Food and Agriculture Organization in South Sudan. 

"We can only mitigate the disaster, but the disaster will still be ongoing without peace."

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Bak, 4, had trouble breathing and was in great discomfort due to severe malnutrition and tuberculosis. His mother, Asunta, said she had no money to pay for proper treatments. CBC News learned Bak died just days after this photo was taken at the children's hospital in Juba. (Stephanie Jenzer/CBC)

He also says the famine areas identified in February aren't the only zones with dangerous food shortages in South Sudan.

"We have a risk in the north of Jonglei," he said, listing off states. "We have a risk of famine also in Aweil. We have a risk of famine in eastern Equatoria and, of course, we have also a risk of the extension of famine in Unity."

Battle in the bread basket

The fighting south of Juba in the bread basket equatorial states has brought food production to a grinding halt, with people forced to leave their homes and livelihoods behind.

Inflation has reached crippling levels, meaning even if food does reach more remote markets, people simply can't afford to buy it.

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Nurse and nutritionist Betty Achan has seen the situation go from bad to worse in Juba, where she works at the children's hospital. She says there’s barely any food in the markets her patients can afford. (Stephanie Jenzer/CBC)

The state children's hospital in Juba is crowded with babies who look as old as the universe as they suffer the effects of acute malnutrition.

"We don't have space. We don't have beds. We don't have the mattresses," head nurse Betty Achan said. "The mothers are sleeping on the ground on blankets, and some are sleeping two on a bed and [the rainy season is coming] so it will be very difficult."

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Tereza Garang, 6, weighs just over nine kilograms. Her mother brought her to the children's hospital in South Sudan's capital, Juba, more than two weeks ago because she feared her child was starving to death. (Stephanie Jenzer/CBC)

Achan says she and other hospital workers haven't been paid by the government in three months.

"There is no money," she said. "There is no food, even in the market, and everyone is in Juba" because the outskirts of the city are too dangerous. 

"So, everyone is confined in one place," she said. 

"You don't know what will happen after three hours. You don't know if you'll live, if you'll eat ... We don't know what's going to happen. We're just counting the days."

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Nurse Betty Achan said Daniel was in urgent need of tests and a blood transfusion when his father, Moses, brought him to the hospital. He died overnight Sunday. (Stephanie Jenzer/CBC)