Iren Gitta Kellner was a teenager when her parents, eight siblings and hundreds of other Jews in their Hungarian town were ordered to the train station with suitcases and crammed into cattle cars by national railway workers who looted their bags on the platform.

She was sent to Auschwitz, among the more than 400,000 Jews in Hungary who were deported to the concentration camp in German-occupied Poland over six weeks in 1944. It was a notoriously brutal period of the Nazi campaign to eliminate European Jewry in World War II. Ultimately, about two-thirds of Hungary’s 800,000 Jews were killed.

Ms. Kellner survived, making her way to the United States. But for the rest of her life, she recounts in court filings, she woke up screaming at night, the harrowing train ride never ending in her nightmares. And she spent her final years fighting — unsuccessfully — for some justice, suing Hungary’s national railway for its participation in the genocide.

Now, a group of other survivors of the Hungarian Holocaust are hoping Ms. Kellner’s failed efforts will help persuade American judges to hear their claims against the national railway in U.S. courts instead. It is not their first attempt, but it may well be one of their last, and could represent the final hope for relief for a dwindling number of living victims of the atrocities in Hungary.

Fighting for survival

Hungary cultivated ties with Germany during Adolf Hitler’s rise in the 1930s and was its ally for most of World War II. It was not until 1944, as Hungary sought to distance itself from Germany, that the Nazis occupied the country and set about systematically killing its Jews.

Hungary “is now preparing for the annihilation of Hungarian Jews by the most fiendish methods,” The New York Times reported that May. By July, Britain’s prime minister, Winston Churchill, writing about the Hungarian Holocaust, said, “There is no doubt in my mind that we are in the presence of one of the greatest and most horrible crimes ever committed.”

Every day for six weeks, four trains, each with several thousand Jews, traveled on the Hungarian national railway to Auschwitz, where most were killed.

More than 75 years later, there has been almost no restitution for the financial losses of Jews in Hungary who managed to escape slaughter and their heirs, and no way for them to seek relief in that country’s courts, lawyers for some of the survivors argued in a filing in a U.S. federal appeals court last month.

Ordinarily, plaintiffs cannot sue foreign governments or agencies like the Hungarian national railway in U.S. courts. The Foreign Sovereign Immunity Act, a 1976 statute, forbids it. But over the last 15 years, a group of survivors has fought a highly technical, drawn-out legal battle in Illinois, arguing that their case falls under one of the few, narrow exceptions.

Exhausting all options

One of those survivors, Paul Chaim Shlomo Fischer, first sued the national rail company and some of Hungary’s banks in federal court in Illinois in 2010. He filed his claim on behalf of a group of Hungarian Holocaust survivors who would end up joining as part of a class-action suit.

But they were rebuffed by both lower and appellate courts, which said that international law favored the “exhaustion” of domestic remedies. The suggestion was that the claims should first be addressed in Hungary.

So in 2016, Ms. Kellner, at age 92, traveled back to her homeland to try to do just that. She sued the national railway in a Budapest court, seeking damages for its participation in the genocide and in theft of her family’s possessions. Her claims were denied, partly because the offenses were deemed too old to litigate.

She then moved to reopen the Illinois class action, arguing that although she was not named in Mr. Fischer’s original suit, she was a member of the class of victims he was trying to establish. Her experience in Hungary, she said, showed that they could not get justice there.

The court rejected her application, saying she lacked legal standing in the Fischer case. When Mr. Fischer tried to appeal that ruling, he, too, was told he had no standing — this time in Ms. Kellner’s case.

Still, the appellate court said it was “sympathetic” and suggested they try again by refiling a new complaint in the lower court.

When they did, the lower court said it was waiting to hear the Supreme Court weigh in on other cases involving exceptions to the Foreign Sovereign Immunity Act.

To qualify for some exceptions, plaintiffs (like the survivors of the Hungarian Holocaust) must first show a business connection between the foreign defendant and the United States, among other requirements.

Last year, the Supreme Court rejected a suit involving another group of Hungarian Holocaust victims. They argued that their case qualified because their stolen property had been liquidated and mixed with Hungarian assets that were later used to fund bond issuances and make military purchases in the United States. The justices concluded that the connection between the war thefts and money Hungary spent in the 21st century on American soil was too loose.

Richard Weisberg, one of the lawyers representing Mr. Fischer, said their case was different because it relies on an exception that does not require tracing the stolen assets into the United States. If the case is allowed to proceed, however, the plaintiffs will still have to show a “commercial nexus,” essentially that Hungary’s national railway generates revenue in the United States, according to Mr. Weisberg.

A lawyer for the Hungarian national railway did not respond to requests for comment.

Whatever happens in the U.S. courts, Ms. Kellner will not get relief. She died late in 2017.

“She never lived to see a measure of justice in this case, but her courageous lifetime is a reminder that we must never forget the millions whose intentional slaughter she did survive to recount,” Mr. Weisberg said.