BAHAI, Chad — The rebels move easily in this sun-blasted border town, coming and going as they please from the battlefields of Sudan's Darfur region, which lies just a few hundred yards away across a sandy, unmarked riverbed.
Last month the Justice and Equality Movement, the most powerful rebel group in Darfur, launched a brazen drive to Sudan's distant capital for the first time in the five-year war, nearly reaching the city before being repelled by government soldiers. On a recent afternoon about a dozen of the rebels reclined in the shade of a mud-walled home in Bahai, sipping cool sodas and making plans to slaughter a goat for dinner.
"Here we can rest, get our vehicles repaired, bring the wounded men to the hospital, before going back to Darfur," said a senior rebel official, Abubaker Hamid Nour, motioning over his shoulder to a border that exists only on paper.
The rebels' free rein along this long, lawless frontier has annoyed Sudan for much of the Darfur war. But last month's attack demonstrated how the war — which already has claimed an estimated 300,000 lives — is escalating into an international confrontation between Chad and Sudan, troubled rivals that sit astride some of the harshest and most restive terrain in Africa.
Sudan immediately cut diplomatic ties with Chad and accused it of sponsoring the attack, a charge that Chadian officials and the rebels themselves deny. But it came just three months after a mirror-image assault by a separate collection of rebels — based in and financed by Sudan — nearly toppled the government in Chad.
On Saturday, Chadian rebels clashed with government forces in Goz Beida, a town surrounded by Darfur refugee camps about 40 miles from the Sudanese border. Chadian officials, who blamed Sudan for the attack, said that the army drove off the rebels and had regained control of the town by nightfall.
Experts say that the regimes — each repressive, militaristic and beset by internal challenges — are bent on destabilizing each other. While few expect all-out war, they say that the confrontation further complicates the Darfur conflict, prolonging the misery of nearly 3 million refugees on both sides of the border.
"It's a proxy war," said Hafiz Mohamed, a Sudan expert with Justice Africa, a London-based advocacy group. "Relations between Chad and Sudan have really deteriorated, and unless you address the Chad-Sudan relationship, you cannot solve the Darfur problem."
The two vast, impoverished nations at the edge of the Sahara were allies through much of the 1990s. But relations began to sour after tribes in Sudan's western Darfur region launched a political uprising in 2003 against the country's Arab-led central government.
Chadian President Idriss Deby's tribe, the Zaghawa, produced some of Darfur's top rebel commanders, and Deby proved unable or unwilling to stop the rebels from operating in the windswept deserts of eastern Chad.
According to the Small Arms Survey, a Swiss research center, Sudan began serving as a haven for Deby opponents in 2004. By late the following year, each country was collaborating intensively with the other's enemies, pumping more weapons and perhaps more fighters into a region that already had too many of both.
Since independence in 1960, every Chadian regime has fallen in a coup, and Deby has faced rebellions ever since he seized the presidency in 1990. Critics say he's responded by consolidating power, silencing political opponents and diverting oil revenues to military projects. Elections are shams. Some of the rebels who want to remove him are former members of his inner circle, including a nephew.
Chadian officials count 27 attacks by Sudan-backed rebels in the past two and a half years, two of which reached the capital.
"We are doing everything to avoid a confrontation, but Khartoum wants to finish us off," said Chad's information minister, Mahamat Hissene.
For all its domestic turmoil, however, Chad has played a largely constructive role in Darfur so far. Eastern Chad hosts a quarter-million Sudanese refugees in United Nations-run camps. A force of 3,700 European soldiers has begun to deploy in the camps to bolster security, and a U.N. mission is training 850 Chadian police officers to do the same, although the international forces say that they won't take sides if rebels again try to take Chad.
In a tour of the region last week, the U.N. Security Council won assurances from Chad and Sudan that they'd adhere to past pledges not to allow rebels from the neighboring country to operate within their borders.
But while diplomats met Chadian officials in the capital, N'Djamena, a group of Darfur rebels was camped out comfortably across the country in Bahai, 600 miles away. They slept on mats in a dirt compound belonging to a sympathetic physician, just a few yards from the home of the local police official. One of their fighters was being treated in the town's medical clinic.
"Sure, there are a few rebels here. They come to buy things or fix their cars," said the police official, Iage Abdallah. "There's no problem."
Although Justice and Equality Movement leaders move freely within Chad — some are fixtures in the lobbies and coffee shops of N'Djamena's plusher hotels — they say they don't operate camps here or receive direct support from the government. However, when N'Djamena came under attack from Sudan-sponsored rebels in February, JEM fighters headed for the capital to back up the Chadian military, rebel leaders and analysts said.
As it turned out, their help wasn't needed; the rebellion fizzled in the face of Chad's superior military arsenal. When the Chadian rebels fled the city, they left behind their Sudan-donated trucks and battlewagons, which Chadian soldiers seized and promptly gave to JEM rebels, analysts said.
JEM leaders said their May offensive had been planned for months and was intended to send a message to political elites in Khartoum, not as a response to the attack on Chad.
"(Sudanese President) Omar Bashir wants people to think that the problems in Darfur are far away and don't concern the people in the center of Sudan," said Nour, the JEM leader. "We wanted to show that either they solve the problems of Darfur or there will be no safe place in Sudan."
Their four-day, 700-mile march from western Darfur to Khartoum's neighboring city of Omdurman — where British forces won control of Sudan in 1898 — stunned Sudanese authorities. JEM's young fighters were unaccustomed to urban combat, however. They scattered after several hours of bloody street battles, never making a serious push into Khartoum.
"I got lost," admitted Hussein Ageid, a 43-year-old combatant in Bahai. He'd been in Khartoum only once before, as a teenager looking for work, and was better at desert warfare.
Nour said the men would regroup and try again. And Sudanese officials remain convinced that Chad is planning to back another strike.
"The attack in Omdurman is proof that Chad is not in a position to fulfill their promises," said Rabie Abdul Atti, a Sudanese government spokesman. "So Sudan reserves the right to take action."