AMNA NAWAZ: International aid groups issued a joint declaration today that the hunger crisis in Sudan is of historic proportions.

For nearly 18 months, the country has been embroiled in a civil war, a war that's killed tens of thousands of people and displaced millions more.

In the fourth report from Sudan's front lines, supported by the Pulitzer Center, special correspondent Leila Molana-Allen met some of the men fighting this war and looked into the powers funding it.

LEILA MOLANA-ALLEN: Elated, defiant, united.

These Sudanese Armed Forces soldiers want to show they're ready for a fight.

In reality, most haven't yet been on a battlefield.

They're fresh recruits, part of the government's drive to grow the army's ranks in the fight against a rebel militia, the Rapid Support Forces.

A shopkeeper, an engineer, and a middle school English teacher, a year ago, these men couldn't have imagined fighting.

Now they gather at this repurposed soccer stadium for basic training, some still wearing sneakers and jeans, waiting for their uniforms.

This is the first time you have ever been in the army?

And, Ahmed, you are an English teacher, and now the first time you are serving as well.

MAN: It will take our lives to defeat the rebellion.

LEILA MOLANA-ALLEN: Twenty-nine-year-old Mohamad Awadallah came here to Qadarif two months ago after the RSF burned and pillaged his home state of Sennar.

MOHAMAD AWADALLAH, Sudanese Armed Forces Recruit (through translator): In Sennar, I saw death.

There were rapes.

The RSF were killing anyone they found in front of them.

The situation in the country is getting worse, and we're afraid of being displaced again to another state.

LEILA MOLANA-ALLEN: In peacetime, he runs a market stall.

These volunteers aren't paid to serve.

The community does what it can to support them.

MOHAMAD AWADALLAH (through translator): The meals are regular but there is no salary.

Our relatives outside Sudan send us money to help us.

LEILA MOLANA-ALLEN: They don't underestimate the enemy they're fighting.

Once a militia armed by the country's former dictator, Omar al-Bashir, to fight rebels in Darfur and responsible for mass slaughter of civilians there, the RSF was absorbed into the army in 2013.

They fought here and abroad, building up strength and experience.

Bashir used them to crack down on popular protests in 2019, after he fell from power, his other elite army units were disbanded, making the RSF all-powerful.

In 2021, RSF leader Mohamed Hamdan Dagalo with army chief Abdel Fattah Burhan to seize power in a military coup.

When war erupted between them last year, the RSF quickly seized major territory like the capital, Khartoum, and much of Darfur.

This year, having rallied the troops, the army has managed to seize some of that territory back, and the army is now purportedly buying weapons from Iran and Russia.

But it's a long, hard, fight, much of it street-to-street urban warfare in densely packed residential areas.

The impact on civilians is devastating.

Up to a 150,000 people have already been killed, and over 11 million displaced from their homes.

The RSF has been recruiting too, but forcibly.

We met several child soldiers kidnapped from their families to serve the militia when it swept through Khartoum.

Bilal is just 15.

We're protecting his identity for fear of reprisals.

He was arbitrarily arrested by militiamen from outside his home and held by the RSF for months.

BILAL, Escaped Child Soldier (through translator): The RSF beat us every day, insulted us, and made us clean their military vehicles.

They would force us to help them steal from houses and take boys to fight with them in battles.

LEILA MOLANA-ALLEN: Finally, his chance came.

BILAL (through translator): They were drunk when I escaped.

We were carrying flour sacks, and they were distracted.

I ran to the main road and found a bus passing by.

I knew the driver.

He was from my neighborhood.

LEILA MOLANA-ALLEN: After hiding with neighbors for two weeks, Bilal snuck across the river by night to SAF territory.

He still doesn't know the fate of those who helped him.

BILAL (through translator): I'm very worried about them and hope they get out.

LEILA MOLANA-ALLEN: A loving reunion with his relieved father.

But these are the lucky ones, their stories of escape miraculous.

They say many more are still stuck in RSF territory.

Foreign actors are staking a claim in the conflict, too, sending a steady flow of foreign weapons into the country.

The United Arab Emirates is accused of sending weapons to the RSF to be smuggled in via Chad.

The United States is one of the leading arms traders to the UAE.

Dotted around the burned-out battleground, Emirati armored vehicles, Russian tanks, some from the Cold War.

These battlefields are awash with foreign arms, some newly imported, some legacy weapons from the wars that have plagued this continent for decades.

Many of the guns now being used in Sudan come from Libya's civil war in 2014.

We found evidence of Emirati and Russian weapons systems as well, Turkish and Serbian munitions as well as U.S.-manufactured small arms.

This is an American-made M47 Dragon anti-tank missile launcher.

The Sudanese Armed Forces say they found many of left behind when they pushed the Rapid Support Forces back.

It's a 20-year-old model, so there's no telling where it's been between then and now.

The serial number, the best way of tracking how these weapons entered the company, has been carefully removed.

Critics say the UAE wants control over Sudan's Red Sea ports and rich mineral mines.

The Emiratis deny supplying and funding the RSF, but have engaged in talks to determine Sudan's future.

Sudan's U.S. envoy, Tom Perriello, invited an Emirati delegation to failed talks in Geneva in August.

The Sudanese army says it will not negotiate with a foreign power that's arming its enemies.

Arms dealing is legal in the right circumstances.

But countries who trade have a responsibility to track where and how their weapons are used.

And these weapons are being used to massacre civilians.

Brian Castner is a weapons investigator for Amnesty International.

BRIAN CASTNER, Amnesty International: Modern ammunition does terrible things to the human body, breaks bones, can take off legs.

You have to look at priorities.

You have to look at whether your priority is making the most money in however way possible.

And what are your responsibility when it comes to human rights?

What's your responsibility is when it comes to stopping crimes against civilians, when it comes to stopping civilian casualties?

LEILA MOLANA-ALLEN: It's not just foreign weapons, but foreign fighters playing a role in this war.

Mercenaries from nearly a dozen countries have been spotted fighting alongside the RSF.

Last month, Emirati passports were found in an area where the militia had been pushed back.

We negotiated rare access to interview some of the RSF mercenaries the Sudanese army has captured at a nondescript intelligence base just meters from the echoing gunfire of the front line.

Loul, from South Sudan, says he never even made the choice to fight.

He came to work in Khartoum because, even in wartime, he had more chance of earning money than back home.

In January, he was kidnapped from his cigarette stall, and told he would be free once he helped the RSF win back Omdurman.

He arrived at the front to discover he and the other young fighters were little more than cannon fodder.

LOUL, Mercenary From South Sudan (through translator): There weren't many soldiers, and no one could use the weapons.

The few people who did fire bullets killed themselves or others in the group by accident.

They were children, too young to fight.

I was afraid, thinking, will I survive or not?

LEILA MOLANA-ALLEN: It was the only battle Loul would participate in, and it didn't last long.

LOUL (through translator): On the way to the battlefront, clashes broke out and I was shot in the leg.

The driver fled.

I was shot again and fell to the ground with some others.

I lay on the ground for four hours.

The people with me died.

LEILA MOLANA-ALLEN: Loul managed to crawl to an abandoned house, where he was eventually found and arrested by the Sudanese army.

He's been held here since March.

LOUL (through translator): I still don't understand anything that's happening.

Will they let me go or not?

No one tells me anything.

Will I go home to my family or to prison?

LEILA MOLANA-ALLEN: Zakaria is just 16.

When an RSF recruiter came to his destitute village in Chad in early February offering cash to fight, he jumped at the chance to help his family.

ZAKARIA, Mercenary From South Sudan (through translator): They said they would pay us when we reached Sudan, $600.

But when we arrived, they didn't give us any money.

LEILA MOLANA-ALLEN: Like all the others here, he never saw a penny.

By April, he'd been captured by the army.

He's been locked up in Omdurman ever since.

Prisoners of war must be treated humanely under international law.

On camera, the boys said they were being treated well.

But while setting up the interview, they whispered to the "News Hour" team that they were being starved and begged for help to get out.

Every member of the group was severely emaciated.

Like Bilal, these are just young boys too, victims of a vicious conflict that spares no one.

It's an cycle of corruption and abuse that threatens to drag Sudan's neighboring countries, already unstable and dealing with multiple crises, into the abyss of war along with it.

And this is the impact of that war, a thriving regional capital in ruins.

Omdurman market used to be the bustling heart of this region.

Millions of locals would come from all around to buy provisions, to socialize, and for anything else they needed.

Now it's abandoned.

Soldiers say they're still digging through the rubble, finding bodies under these charred shop fronts.

And those escaping Khartoum across the river say the devastation there is even worse.

The country's foundations lies in ruins too.

The economy has collapsed.

Children haven't been to school in over a year.

Fear and hunger rule the land.

When this war does end, Sudan's road ahead is full of pitfalls.

It's just five years since popular protests toppled the country's longtime dictator.

But then army snatched power from the people.

While many here support it in fighting the RSF, if they win, the next battle will be for democracy.

The military junta claims it will hand back power when there is peace.

Leaders of civil society resistance committees are skeptical.

ABDULRAHMAN MOHAMMED ALI, Port Sudan Resistance Committee (through translator): I do not believe that the army has no interest in ruling the country.

All the evidence shows the army is interested in staying in power.

The future of the youth is in great danger because, after the revolution, many hopes were built.

And what's happening now is a complete destruction of everything.

LEILA MOLANA-ALLEN: And whoever leads the country, building back from this devastation could take a decade.

So much has been lost, lives, homes, dreams.

In the midst of such suffering, hope for the future, so vibrant just a few years ago, is turning to dust.

For the "PBS News Hour," I'm Leila Molana-Allen in Omdurman, Sudan.