The telegram reached Prime Minister Mackenzie King as he was escorting the Royal Family in Washington in early June, 1939. Now was the time to show “true Christian charity,” said a group of writers, historians and business people, and let the 907 German Jews of the St. Louis come ashore.

But Mr. King said it was not Canada’s problem and left the matter to officials such as Frederick Blair, the architect of Canada’s restrictive immigration policies, known for his inflexibility. “The line must be drawn somewhere,” Mr. Blair wrote in an internal document.

Almost 80 years later, another Liberal prime minister, Justin Trudeau, will apologize to Canadian Jews after Question Period on Wednesday for turning away the desperate refugees of the St. Louis, hundreds of whom would die in Nazi death camps. The purpose, he said last May, is to draw attention to this country’s failings, “as we vow never to let history repeat itself.”