The greasy, stinking Land Cruiser, with its screeching fan belt and goatskin water jug swinging off the back, beat a fast pace across the desert in rebel-held Darfur, until it slammed to a jarring stop.

Riding on the roof was Issac, an energetic sharpshooter from the Sudanese Liberation Army (SLA). He had spotted the target. The Land Cruiser, haphazardly camouflaged with black spray paint, rested quietly for a moment. Issac looked down the sight of his AK-47 rifle. He fired, the crackle of gunshots echoing through the silent desert.

In the distance, a gentle antelope broke for the bush. The famished rebel forces spent the next 45 minutes and nine shots chasing down the swift creature through thorny bushes and thick sand before catching their prey.

Finding food is a matter of survival for thousands of people in this vast area of Sudan, including the warring troops who are fueling a raging humanitarian crisis. Armed conflict in Darfur has left 1.2 million people homeless, 50,000 dead and hundreds of thousands vulnerable to life-threatening diseases.

International condemnation has focused on the government-backed militia known as the Janjaweed, which has terrorized civilians in areas where armed resistance to the state has been strongest. Less attention has been devoted to the SLA rebels, who said they started the conflict to defend the rights of Darfur's African tribes but now preside over corners of acute suffering and desperation on the frontiers of Africa's largest country.

A week spent traveling through rebel-held areas showed the SLA to be an ill-equipped, untrained and disorganized group, with child fighters among its ragtag ranks. Its grand ambitions are not matched by its resources. The only thing the rebels don't seem to be lacking is motivation.

"Give us 500 cars with mounted machine guns and we'll take Khartoum in one month," proclaimed Bahar Ibrahim, a top adviser in the SLA's political wing, referring to Sudan's capital. A graying wisp of man, Ibrahim said over sugary tea at a base camp in the town of Bahai that he admired the ferocity of American action movies and spaghetti westerns. "We can act like that," he said.

Yet on that steamy afternoon, the rebels in the SUV weren't able even to cross a riverbed that had swollen with slow-moving water from seasonal rainfall. At the base camp, they had five cars, all taken in battle from the government. Not one of them would start.

While the Janjaweed is united by ethnic hatred toward African tribes, SLA leaders speak with equal ferocity about the Arab government in Khartoum, which they say has discriminated against generations of black Africans. They see themselves as heroes defending the lives of tribal members who have not fled to disease-ridden camps that the government runs.

As a result, SLA leaders, like the commanders of the Janjaweed, refuse to silence their guns. Peace talks in Nigeria between SLA rebels and the government stalled last week, as the sides argued over who scuttled attempts at a cease-fire.

In the last week, 3,000 people have fled more fighting in the town of Zam Zam in North Darfur, a U.N. report said. It was not clear if rebels or Janjaweed sparked the clashes. The United Nations had set an Aug. 30 deadline for the government to improve safety conditions and rein in Janjaweed or face unspecified sanctions.

The U.S. government is pressing for sanctions unless the militias are brought under control, while some members of the U.N. Security Council say that Sudan should be given more time. On Thursday, Secretary of State Colin L. Powell is scheduled to testify before the Senate Foreign Relations Committee about the findings of a U.S. investigation into whether genocide is being committed in Darfur.

Meanwhile, civilians continue to suffer. The rebels are accused of atrocities, although on a much smaller scale than the Janjaweed and its government sponsors. The rebels control a vast countryside where an estimated 130,000 civilians are beyond the reach of food and medical aid that those in the government-held areas are slowly receiving.

The SLA hadn't planned to gain so much ground so quickly. The group claimed its first major victory last year in the stunning capture of the town of El Fasher. The rebels killed 75 government soldiers, stole weapons and destroyed four helicopter gunships and two Antonov aircraft, government officials said. A second, smaller rebel group called the Justice and Equality Movement (JEM) joined the fight against the government.

The government in Khartoum reacted to the defeat by arming the Janjaweed to assist the army. The Sudanese military launched a bombing campaign against hundreds of largely African villages, leaving more than 1 million people as refugees.

The Darfur conflict emerged just as a U.S.-backed peace between the government and separate rebel groups in the south of Sudan promised to end nearly half a century of intermittent warfare there. The SLA asked to be a part of those peace talks, but the government refused. Now, the government faces yet another uprising mounting among the Beja tribe in eastern Sudan.

The SLA leaders are drawn from the elite ranks of African tribes, some of whom say they are fighting the legacy of decades of discrimination for more political power and a share of Sudan' s $1 million-a-day oil revenue. Some leaders say what they really want is to join with other rebellions around Sudan and push for a change of government in Khartoum. However, the groups have little political experience and remain fragmented.

In the town of Faraywaiah, SLA rebels explained their struggle by pointing to a ravine where 12 male bodies lay decomposing. One body was curled up in a fetal position. Another's scalp was rotting in the hot sun. Others had skulls poking through burned hair. The bitter smell of the dead hung in the hot air.

The rebels and a few townspeople who are left said that these were local African men, some of them caught by surprise at the village well and killed by government forces who stormed the town in March. The town, pockmarked with bomb craters, was deserted.

A Star Among Warriors

The rebels' most famous fighter is known as Kongo. He arrived one afternoon in the shade of a tree where his troops had spread carpets for an afternoon nap amid Belgian assault rifles and ammunition belts. Kongo had a thick swagger. His nom de guerre means the man who walks without a stoop.

His men gave him this name because they claim he never cowers from gunfire. That might explain why his left eye is shot out, a bullet is lodged in his jaw and one of his legs is stitched like a pincushion.

Kongo had a pounding headache and asked a reporter for some aspirin and a bottle of pastis, an aniseed-flavored, French liqueur, to soothe his aching head. The SLA's star fighter embodies the disparity between the group's determination and its resources.

Last July, Kongo fought in Gourbou Jong, a battle the SLA calls its mini-Stalingrad, after the Soviet defeat of Adolf Hitler's army. Gourbou Jong proved that despite poor training and bad weapons, the rebels could beat one of the most powerful militaries in Africa. A Sudanese Army general was killed in the fighting.

Kongo, whose given name is Kitir Zakariya, is nominally a commander in the SLA. But to his troops he is a god. He removed his sunglasses and revealed a wounded patch of skin where an eye used to be and described his mission to fight the Arabs in Darfur.

"The only language they understand is the gun," Kongo said, fiddling with his charm necklace, dozens of worn, square leather pouches filled with Koranic verses to protect him from gunfire. Then he took a cigarette out of his pocket.

"We, the youth of African tribes in Darfur, feel this has been going on for years. Something must be done," he said. "We can take them with just a few cars."

Listening to his every word was baby-faced, curly haired Harry Fadhul, who possessed a large gun and a frown. He's one of many young fighters who have chosen combat over being raised in squalid and humiliating refugee camps. Sipping powdered milk loaded with sugar, he recounted how he joined the force three months ago, after his village was burned. He saw corpses everywhere. His mother fled to a refugee camp, he said.

"I have nowhere to go," said Fadhul, who gave his age as 18 but looked much younger. "The SLA is my family now."

Kongo justified the war by describing the way successive governments in Khartoum discriminated against African tribes, punishing students in school who spoke their tribal language, Zaghawa. The SLA is now renaming towns from Arabic to Zaghawan.

"Whenever the Arabs talked to you it was like they were better than you," he said, a hand resting on the pistol in his belt holster. "No one seems to think they could ever live peacefully with their Arab neighbors again. I don't have any Arab friends. I would never marry even a beautiful Arab woman now. She is not for me."

African tribes in Darfur have festering grievances dating back to the formation of a movement known as the Arab Gathering in the 1980s. Bringing together various Arab tribes, it espoused the supremacy of the "Arab race" and laid plans to help Arab tribes in displace African tribes that were granted land under British rule. Heavy clashes began in 1987.

In the early 1990s, the country's southern rebel movement, the Sudan People's Liberation Army, trained rebels from Darfur and deployed forces in the region to fight the government. But the rebellion in Darfur was quickly crushed.

In response to the Arab Gathering, a group of African intellectuals created the Black Book, a fiery catalogue of facts and figures secretly gathered from government records that sought to prove that three Arab tribes dominated positions of power in nearly every sphere of Sudanese society, including hospitals, schools and police forces. Copies were passed out to every government leader, including the president, causing a stir in Khartoum.

It was a sign of what was to come. Today several authors of the Black Book, who called themselves The Seekers of Truth and Justice, are leaders in the SLA and JEM.

"We know there is a well-organized plan to get rid of us," said Ibrahim, who helped advise those who wrote the Black Book. "But we are warriors; that is our culture. The Arabs here don't know how hard we are willing to fight for our land."

The challenge for the SLA is not only to confront the powerful regime in Khartoum, but to somehow administer a territory where a hidden humanitarian crisis is underway. Part of the rebels' popular support will be based on how they feed and protect their own people, analysts said.

Nowhere to Turn

In an open field ringed by red mountains, Hawi Bas and her three children were hiding on a recent day under a scrubby tree in Shiga Karo, a rebel-held village about 70 miles east of Sudan's border with Chad.

Her youngest child, 2-year-old Hari, had wilting hair and willowy legs. He had become so thin that he could no longer walk. His name means "strong" in Zaghawa. His family survives on boiling the toxic pea known as mukheit, which needs to be soaked in water for three days. But mukheit only fills the stomach; it does not provide real nourishment to children.

Hawi Bas said she could not travel to the safety of refugee camps in Chad. "How are we going to go there?" she asked, crouching in the hot sand and showing a small bowl of mukheit. "We are not feeling fine. I always feel stomach pains. Do you see our condition?"

Aid groups say they believe there are tens of thousands of people struggling to survive in rebel areas, sealed off from aid. The government will not permit aid agencies to travel into rebel-held areas, arguing that the SLA will steal the food. The U.N. food agency has recently been granted access by rebel groups to study the needs in the region, entering through Chad or circumventing government troops.

Refugees say the rebels have not bothered them. Late last month, rebel soldiers distributed sacks of corn flour to some of the displaced, but it was not enough. Hari looked close to death.

Ibrahim, the SLA leader, looked at the child, held him up and then promised to make some calls to aid agencies to work on getting them here to help the refugees.

The rebel group is now suffering from splits within its leadership, and the people can sense a lack of focus. "They seem to have as little as we do," said Ismael Hagar, 25, a teacher who has brought biscuits to the refugees.

On a recent afternoon, the riverbeds were flooded and the only way to cross back into Chad from Sudan was to swim through the dirty water and wade through the mud. Walking alone in the opposite direction was Kongo. He was carrying a burlap sack and his pants were rolled up to his bony knees. He said he was hungry and went to Chad to get meat.

Now after eating, he trudged back across the border.

"To fight," he said. "Always."

Rebels of the Sudanese Liberation Army hunt a wild bird in Sudan's embattled Darfur region, where finding food is a matter of survival for thousands of people.Haron Osman Ali, left, and other rebels with the Sudanese Liberation Army pass the time just across the border from Chad near their base in Bahai. The rebels are unequipped and untrained.Many newly recruited rebels are young, including Mohamed Bokhet, 17, front, Mohamed Dood, 14, left, and Mobarik Idris, 20.SLA rebels pass the remains of civilians who they say were killed by the Sudanese military in the area of Faraywaiah. SLA leaders speak with hatred of the Arab government in Khartoum.