Nawaf and other migrants attempt to reach the channel tunnel to Britain from the migrant camp in Calais, France. (Shannon Jensen/For The Washington Post)

With whoops and with whistles, they emerged from the “Jungle” just as the unseen sun dipped low on a horizon painted in shades of gray.

At first, just a few clambered up the muddy embankment leading to the highway. Then dozens. Then a crowd of hundreds, all desperate to halt the speeding traffic long enough that maybe a lucky few could stow away on a truck. From there, the dream that has drawn thousands of asylum seekers to this gritty French port town would lie within reach: a new life in Britain.

But the riot police were ready. As rocks rained down on the helmeted officers, tear gas canisters came sailing back. Coughing and running through toxic plumes, the crowd retreated to the Jungle, that cauldron of poverty, disease, violence and frustrated ambition.

Calais, separated from Britain’s White Cliffs of Dover by a mere 21 miles, has been the reluctant host of a multinational migrant colony for well over a decade. But ever since Britain and France enacted much tougher security measures at the end of August, it has become a pressure cooker with no release valve.

Day by day, more people move in, one stream in the rivers of humanity that have flowed this year from the Middle East, Africa and South Asia, inundating Europe.

With miles of new barbed-wire fences, squadrons of heavily armed police and packs of specially trained sniffer dogs all contributing to this town’s fortresslike feel, fewer and fewer people are getting out.

Makeshift shelters stretch throughout the “Jungle” migrant camp in Calais, France. (Shannon Jensen/For The Washington Post)

The result is a combustible mix: a growing population of people who don’t want to be here and who despair that they will never be able to leave. More than perhaps anywhere else on Europe’s migrant trail, the mood here is increasingly defiant, with asylum seekers becoming ever bolder in their attempts to challenge security forces head-on and break through the tightening cordon that prevents them from reaching Britain.

One of the most troubling incidents for authorities came last weekend, when 200 migrants broke into Eurotunnel’s French terminal, clashing with police and prompting an hours-long suspension of the undersea rail service linking the two countries through the Channel Tunnel. John Keefe, a Eurotunnel spokesman, said the “very aggressive and very organized” attempt represented “a different kind of tactic.”

“If they can’t get through on their preferred route without violence, will they then use violence to get through?” he asked. “There has never been any anger before, but this was: ‘We don’t care. We are going through.’ ”

The grim conditions in the Jungle — the name the migrants have given their sprawling encampment on the outskirts of town — help explain why they’re so determined to get out.

In the Jungle, set in flood-prone scrubland within sight of the English Channel, whiffs of salty sea air mix with the scents of human waste and burning trash. People who have fled war or despotic regimes in Syria, Iraq, Afghanistan, Eritrea and Sudan find themselves sleeping on cold, damp French soil, with only leaky plastic tents to shelter them from the elements. Inter-ethnic rivalries and disputes over black-market business deals lead to frequent eruptions of violence.

Calais, France.

“It’s the worst slum in Western Europe — maybe even in all of Europe,” said François Guennoc, a camp volunteer with the aid group L’Auberge des Migrants. “The French and British governments should be ashamed of this situation.”

And yet, it is looking ever more permanent, with makeshift shops selling a variety of goods, from cellphones to bicycles; restaurants; three mosques; a church; a theater; and even several “hotels” that offer, for a price, a bit of padding to sleep on and guaranteed protection from the rain. Whereas migrants once moved in and out of Calais in a matter of days or weeks, many have found themselves stuck here for months. The population is estimated to be at least 4,000 and grows by the day.

For Nawaf, a 23-year-old camp newcomer, “every day in the Jungle is like a year.”

“All my life, I’ve slept in my own bed with pillows,” said Nawaf, a stylish Syrian who sports hipster glasses and a black leather jacket. “I’ve never dreamed of something like this.”

And yet, Nawaf, who insisted that his last name not be used because he fears for the security of his family in Syria, said he remains determined to reach Britain — at least for now.

Like many here, Nawaf said he believes life in Britain offers better career and education prospects than anywhere else he can go in Europe. Plus, he already speaks English.

“Germany and Austria offer a very good life,” he said. “But they have a very hard language.”

So as Nawaf followed the migrant trail this fall, he bypassed those two countries and kept going until he hit the end of the road in France. From the Jungle, he can see the British coast — but getting there is another matter.

Both day and night, he walks for hours along train tracks, scampering over fences and seeking to evade the notice of police officers who always seem to be blocking his path, no matter how far he roams. The trains rumble by, but Nawaf can only watch longingly.

On one of his first nights in Calais, he managed to slip into the undercarriage of a truck bound for Britain. The smell of turning gears and racing asphalt mingled with the Versace Eros perfume that Nawaf wears, believing that dousing himself in the sweet-smelling spray will throw sniffer dogs off his trail.

But when the truck pulled up to a checkpoint, the police weren’t fooled.

“Come on!” barked the officer, shining a flashlight in Nawaf’s eyes and motioning for him to exit. He did — and then started looking for another truck.

There are easier ways to get to Britain. But they cost the sort of money that few here can afford to pay.

Jungle residents say that for 8,000 British pounds, or about $12,000, smugglers will produce a fake passport and a plane ticket. For $8,000, you can get a ride in the trunk of a car. For $3,000, a smuggler will break the lock on the cargo door of a truck and close it behind you once you’re aboard.

In the French port of Calais, the “Jungle” refugee camp is home to more than 4,000 people. With tough new security measures, it is almost impossible to get out. People are desperate to reach Britain, and they are increasingly challenging French security forces blocking their paths. (Griff Witte and Jason Aldag/The Washington Post)

The prices have risen sharply as the security gets tighter, and the route to Britain becomes ever more perilous. At least 19 people are believed to have died this year attempting to cross, with drowning, electrocution and falls from trucks or trains among the myriad causes.

Dozens of other people have been badly injured. In the Jungle, people clutch maimed limbs and hobble about on crutches — the legacy of failed attempts to cross or, increasingly, of clashes with security forces.

“The police beat me,” said a Syrian man whose arm was wrapped tight in a bright-blue cast.

Rafi Khan, a 20-year-old Afghan, nearly had his legs crushed beneath the wheels of a moving train when he slipped while trying to climb aboard. Instead, he was badly cut as he fell beside the tracks. But his 15-year-old friend wasn’t so lucky a few weeks later: A jolt of electricity killed him instantly.

Still, Khan, who said he fled Afghanistan when the Taliban discovered that he was working for the U.S. Army as an interpreter, is undeterred. He has been living in the Jungle for three months and said he will stay as long as it takes to get to Britain, where, like many others here, he has family. His cousin in Manchester promises that a job as a pizza deliveryman awaits him.

“I won’t stop. I won’t give up,” he said. “We’ve faced a lot of troubles in Afghanistan. This is nothing.”

Nawaf watches two refugees who jumped a fence at the ferry port in Calais, France. They exited 10 minutes later without finding a further way in. (Shannon Jensen/For The Washington Post)

Nawaf, however, has been feeling a little less resolute. Even as the Syrian continues to stalk the train tracks day and night, he is asking friends about Sweden.

Nawaf has a birthday coming up, his 24th. One way or the other, he’s determined not to spend it in the Jungle.

Shannon Jensen and Cléophée Demoustier in Calais and Karla Adam in London contributed to this report.

Read more:

A small town in Slovakia held a vote on accepting refugees. 97 percent said no.

In a Belgrade park where migrants are camping: Hope, confusion and mud

Nearly a third of migrants in Germany claiming to be Syrians aren’t from Syria

Read: full coverage of the Post’s coverage on the refu­gee and migrant crisis