Rohimullah stood at the precipice of this vast tent city on Friday, chest heaving, eyes reddened by exhaustion, his hunchbacked mother-in-law cradled in his arms. He'd carried her for five days. She'd winced and whimpered at every step. 

The rest of his family had arrived days earlier, and their reunion was imminent. Moving toward the plot his relatives had carved out of a hillock to camp on, they passed thousands of fellow Rohingya refugees building homes for now that may become homes for much longer. 

Almost half of the 436,000 Rohingya who have fled a scorched-earth campaign by the Burmese military over the past month now live in and around Balukhali, and the tent city grows by the minute. They are part of the most rapid exodus from any country since the Rwandan genocide in 1994. The sudden crush of nearly half a million people has left Bangladesh's government, aid agencies and refugees themselves totally overwhelmed.

To Rohimullah's left as he walked, women crafted a mud staircase leading up to a whole neighborhood of tents still under construction. To his right, sweat-soaked men hauled bundles of bamboo and tarpaulins to tracts farther afield. Under his feet were the freshly laid bricks of an arterial road.

His pace picked up in the final stretch — up a hill, along a ridge, until finally his family came into sight. He laid his mother-in-law down in the tent, where she wordlessly fell asleep. He lit a cigarette. Before him, undulating hills of tents spread out as far as the eye could see.

Rohimullah carries his mother-in-law into Balukhali in Bangladesh on Sept. 22. (Max Bearak/Max Bearak/The Washington Post)

"It just keeps hitting me that we've made it, and we're in Bangladesh," said Rohimullah, who is 25 and, like many ­Rohingya, uses only one name. "We're safe now."

Though they've escaped their burning villages, a longer ordeal is just beginning for most Rohingya survivors. Since violence in Burma's Rakhine state flared on Aug. 25, thousands, even tens of thousands, have arrived here each day. The flow has slowed in recent days, but the dizzying task of feeding, sheltering and administering medical care to so many people is just getting started.

The most overwhelming aspect is the sheer scale. Balukhali has essentially merged with Kutupalong, an adjacent camp that is home to more than 200,000 Rohingya who fled similar ethnic violence in the early 1990s. Together they account for nearly half a million people, making the area one of the largest and densest refugee concentrations in the world.

Only about a fifth of the new arrivals have received an official food ration, which consists of rice and fortified biscuits. Aid agencies warn that existing water sources could be drained dry in just a few months. Nearly 100,000 children have no school to attend and are instead helping their families fight for whatever aid they can get.

"I don't think it is even possible to understand the scale we are dealing with so suddenly," said Mainuddin, a local government official who is coordinating relief efforts and also uses only one name.

That coordination is complicated by the thousands of well-meaning Bangladeshis who have descended upon the camps to disburse donations. The big organizations — the World Food Program and other U.N. agencies, for instance — have set up relief centers within the tent cities where refugees stand in long yet disciplined lines for aid, but the local effort is much more chaotic.

Tents provided by the UNHCR stand at the Balukhali refugee camp in Cox’s Bazar, Bangladesh, on Sept. 21. (Ismail Ferdous/Bloomberg)

Members of Bangladeshi civic and religious organizations have commandeered trucks and filled them with food packets and used clothing. They either park near the camps and toss donations to the desperate refugees who crowd around them, or simply chuck the donations out of their moving vehicles. 

The Bangladeshi government has set aside 2,000 acres of public land in Balukhali, where the military is gearing up to build a sprawling refu­gee camp that it hopes will be more organized. But construction has barely begun, and a report issued by a group of aid agencies said the land is currently "not suitable for habitation." It could be six months or more, too, before most refugees receive biometric identification cards that would streamline the aid distribution process. 

"These settlements are essentially rural slums," said Kate White, the emergency medical coordinator for Doctors Without Borders. "There are no roads in or out of the settlements, making aid delivery very difficult. The terrain is hilly and prone to landslides, and there is a complete absence of latrines. When you walk through the settlement, you have to wade through streams of dirty water and human feces."

Fearing the spread of disease and the pandemonium more than 430,000 mostly destitute refugees could cause in Bangladesh's already overcrowded cities, the government has imposed strict restrictions on Rohingya mobility. None are allowed beyond a checkpoint on the road north from Balukhali. About 5,100 have already been turned back, according to local police.

Thus confined, refugees in Balukhali are mulling the likelihood that this place will be their world for the foreseeable future. 

No one thinks the Rohingya will return to Burma anytime soon. The memory of what befell their villages is too raw. Nearly every refu­gee interviewed by The Washington Post said their home had been burned down. Some recounted killings and gang rapes. Peter Bouckaert, Human Rights Watch's emergency director, tweeted Friday that stories of atrocities he'd heard firsthand were "so terrible my notebook is stained [with] tears."

Plumes of smoke continue to rise from villages in Burma, visible from the Bangladeshi side of the estuary that divides the two countries. Many refugees are wary of ever attempting a return because of widespread reports that the Burmese military has planted land mines along much of the border. Human Rights Watch released an investigation Saturday in which refugees claim they also saw Burmese soldiers put land mines along roads in Rohingya villages as they fled. Burma's government has denied any role, suggesting that Rohingya militants laid the mines.

The Rohingya are also not Burmese citizens despite having been settled in the country, which is also known as Myanmar, for centuries. The Burmese government has said that only those Rohingya with verifiable ties to Burma will be allowed back, but their systematic disenfranchisement means most won't meet that requirement.

"We are sorry for them, of course," said Mainuddin, the local government aid coordinator. "But we must consider them as temporarily in Bangladesh, not permanently. I cannot say how long they will stay. Until that time, we will have to feed them. There is no other way."

Mushfique Wadud contributed to this report.