KECSKEMET, Hungary — Before Europe felt the full impact of hundreds of thousands of people fleeing war and starvation in Africa and the Middle East, before anti-immigrant populists swept to power in Europe and America, and before the Brexit vote, a series of migration tragedies defined the summer of 2015.
Day after day, people died trying to reach refuge in Europe by land or sea, and in August came one of the most horrific cases: police officers found the decomposing bodies of 71 migrants in a locked truck, abandoned beside a highway in Austria. The victims were left there to die in a grisly crime that shocked people across the Continent and beyond.
On Thursday, a group of smugglers who the authorities said were responsible for the deaths was convicted by a Hungarian court. Four were sentenced to 25 years in prison, and several others received sentences from three to 12 years.
The tragedy unfolded as the largest flow of refugees in Europe since World War II reached crisis levels, and a summit meeting of the continent’s top leaders was convened in the Hofburg palace in Vienna. By August, more than 2,500 men, women and children had drowned making the treacherous voyage across the Mediterranean in rickety boats and rafts that year, and an untold number had died trekking across the Continent.
As politicians debated what to do, before dawn on Aug. 26, a desperate group of 59 men, eight women and four children from Afghanistan, Iran, Iraq and Syria were herded into a refrigerated truck in southern Hungary. Smugglers had promised safe passage to Germany.
Three hours later, the migrants were all dead. They were found the next morning, in sweltering heat, on a highway leading to Vienna, just 31 miles or so from the Hofburg.
Days later, a visibly shaken Chancellor Angela Merkel announced that Germany would open its borders to those clamoring to get into the country — a policy decision that reverberates across the Continent to this day. Italy recently refused entry to a rescue ship carrying hundreds of migrants, and an increasing number of European Union nations adamantly oppose any plan requiring them to share the responsibility of sheltering refugees and asylum seekers.
Beyond the politics, though, the case in Hungary offers a reminder of an unavoidable fact: Desperate people will take desperate measures, even if it can cost them their lives. The tragedy also highlighted how many people, including some former refugees, had taken advantage of the crisis to enrich themselves by turning humans into cargo.
The ringleader of the smuggling network on trial was Lahoo Samsooryamal, a slim, 31-year-old Afghan who speaks eight languages. Mr. Samsooryamal arrived in Hungary in 2013 and made his way to the top of an established network that transported groups of three or four people into Germany or Austria for around 3,500 euros, about $4,100, per head.
In 2014, some 200,000 people sought refuge in Europe from Africa and the Middle East. But in the first six months of 2015, more than 300,000 people flooded onto the Continent.
For smugglers, more refugees meant more business.
“The lure of money quickly pushed them to bigger groups that finally led to the tragedy,” said Gabor Schmidt, the prosecutor, during the trial.
With the help of Metodi Ivanov Georgiev, a Bulgarian who was already being sought by police in his own country, the smugglers established a network of drivers — poor Bulgarians, often from Roma villages.
Soon, they were operating on an “industrial scale,” Mr. Schmidt said, moving 1,200 people in 31 trips that began at the Hungary-Serbia border.
Mr. Samsooryamal’s ring was part of a broader international network, according to prosecutors. As migrants increasingly sought to travel from the western Balkans to European Union countries — with their open borders and economic promise — crime syndicates in each country worked in coordination.
For those seeking passage across Europe, smugglers were relatively easy to find, as migrants passed phone numbers between friends and families. Mr. Samsooryamal’s group was unaware that the authorities had also gotten their numbers, and were listening to and taping their phone calls.
Those recordings, played in court, revealed that everyone involved knew how desperate the situation was for those in the truck in the hours before they died.
Just 20 minutes into their journey, the driver suspected something was wrong and called Mr. Georgiev, who told him not to stop.
Forty minutes into the trip, the smugglers pulled into a gas station to get water for their human cargo — something they had forgotten to do. But when they saw police officers nearby, they decided not to open the truck and not to give the people anything to drink.
The driver called the boss again, reporting that the passengers “knocked like hell at the gas station.”
As the screams from the back of the truck grew louder, the driver and his partner grew increasingly terrified, according to testimony.
They called Mr. Samsooryamal, who usually had the cellphone number of someone in the groups that he was smuggling. He had not done that this time, however.
There were more panicked calls between the bosses and the driver, who noticed that the passengers were trying to bore a hole out of the box to get air.
An hour and 20 minutes into the trip, the screaming continued, with the driver clearly able to make out one word, repeated over and over: “Please.”
Around this time, in a call between Mr. Samsooryamal and Mr. Georgiev, Mr. Samsooryamal finally lost his temper when told that the women would not stop wailing.
“If he opens, I know what will happen,” Mr. Samsooryamal said. “He should know for sure everybody will go out. He should know that if he doesn’t want to end in jail, he shouldn’t open.”
Running low on gas and panicked, the driver decided to just abandon the truck on the side of the road.
At the trial, Mr. Samsooryamal was unapologetic, insisting that the migrants chose to make the journey and knew the risks.
“I know well what kind of difficulty being a migrant goes with — you play with death and you’re ready to do it,” he said, relating his own story of being smuggled through Turkey in 2009.
He acknowledged being part of the smuggling group, but said he was just a “middleman on the phone.”
“I was nobody’s boss,” he said. “Giving information is not giving orders. I didn’t create this crime group, it was not in my hands.”
Helene Bienvenu reported from Kecskemet, and Marc Santora from Warsaw.