LONDON—Four men were given long jail sentences on Friday for the manslaughter of 39 Vietnamese men, women and children who suffocated to death in a stifling, airtight shipping container in October 2019 as they were being smuggled into Britain. The discovery of so many dead people—two as young as 15—in the back of the truck on an industrial estate to the east of London shocked Britain and Vietnam. It also shone a spotlight on the illicit global trade that sends the poor of Asia, Africa and the Middle East on perilous journeys to the West. As oxygen levels fell, some tried desperately to escape, but in vain. Others used mobile phones to say their last farewells to devastated relatives on the other side of the world. Judge Nigel Sweeney said they had suffered an “excruciating slow death” as he jailed seven men involved in the people smuggling gang for a …