– Harold Katz didn’t require a crash course in Hebrew before his bar mitzvah this week in Wilmette, Ill. He started preparing 76 years ago, and his skills never got rusty.

Katz, 89, who lives in a retirement home, was to have celebrated the occasion in Czechoslovakia back in 1941. But that plan — like so many others — was upended by the Holocaust. The Nazis murdered his father, mother, three brothers and four sisters.

Now his bar mitzvah, the Jewish ceremony that marks the transition to manhood, takes place under the shadow of a theological puzzle.

“Why did God let this happen?” he asked. “For all these years, I’ve been asking that. I will never understand.”

One brother survived the Holocaust. Katz’s own survival came through a chain of happenstance. If a single link had broken, he wouldn’t be spending Memorial Day reading from a Torah scroll he commissioned and in a synagogue — Chabad of Wilmette — built of imported Jerusalem stone that he donated.

Virtually every building in Jerusalem is clad in it. When the sun hits at the right angle, the city shimmers.

Amid the horrors of the Holocaust, Katz desperately wanted to take refuge in Jerusalem, but the Germans were determined that he wouldn’t escape, and the British were determined that he wouldn’t reach Jerusalem.

At the time Katz’s bar mitzvah was originally scheduled, his hometown of Tarn, Czechoslovakia, was occupied by Hungarian troops allied with Adolf Hitler.

“They went up and down the streets, ordering the Jews to get dressed quickly and come to the synagogue,” Katz said. “I remember it as if it was yesterday. The trucks coming down the street.”

They were taken to a larger city and, eventually, across the border to Poland. There they were ordered out of the trucks and left beside the road.

His father had a sister living in Poland, and Katz’s family moved in with her. Then his father thought they had a better chance of surviving back in Czechoslovakia. He took the family across the border to Chust, as they feared being recognized in their hometown.

A Hungarian woman offered to smuggle Harold Katz into Budapest. Katz’s father didn’t object. The rest of the family remained in Chust. In 1944, they were sent to Auschwitz, where more than a million Jews were killed. “I think: ‘Why didn’t I save them?’ ” Katz said. His daughter, Lila Katz, said it’s futile to reassure her father: “I tell him: ‘You were a boy, barely 13. What could you do?’ ”

In Hungary, Katz made contact with an underground Zionist group that provided him with false identity papers. He posed as a member of the Hungarian army’s youth group. “Three times I was caught,” Katz said. “And three times I got away.”

But he couldn’t escape Nazi-occupied Europe. In 1944, he was on a list of people awaiting passage to Palestine, but the boat sailed before his number came up.

As the war was drawing to a close, he was hiding in an abandoned building in Budapest. So, too, he said, was a deserter from the German army, who bragged about killing Jews.

Liberated by a Russian detachment, Katz told the Jewish commander about the German in the building. He said the Russian soldiers dragged the German out and blindfolded him. The commander handed Katz a pistol.

“I shot him in the back,” Katz said. Did that dissipate his anger? No, he replied. To this day, he feels it.

Katz, then 17, assumed that the rest of his family was dead until a survivor of Auschwitz said Katz’s oldest brother was alive. Harold and Maurie Katz found each other, then joined the displaced persons wandering Europe after World War II.

When one fellow traveler said he was going to New York, Harold Katz recalled that his mother had relatives in the United States. So he gave the fellow an ad to place in a Yiddish newspaper published in New York. “I’m looking for my uncle and aunt,” it began.

An aunt and uncle in Chicago happened to read the paper the day the ad ran. They sent Harold and Maurie a telegram, followed by a food package, then airline tickets.

Harold found work as a sewing machine operator while Maurie learned the building trades. He established a construction business, and Harold joined him. They built homes all over the Chicago area.

Along the way, Harold learned English at the Jewish People’s Institute, a West Side community center. There he met his wife, Judy, a survivor of Auschwitz. They had a daughter, Lila, and two sons.

Lila Katz said her parents didn’t talk about the Holocaust until 13 years ago, when she saw a movie about Budapest in World War II. “I knew my Dad had been there, so I told him: ‘You’re going to show me Budapest,’ ” Lila Katz said.

Last year, the family threw a birthday party for Katz. “My dad got up and, out of the blue, announced: ‘I’m going to have a bar mitzvah,’ ” Lila Katz said.

And so he will. The celebration is scheduled to begin today, with the completion of the Torah scroll that Katz commissioned. By tradition, the final letters will be written in memory of congregants and friends’ loved ones.

There is a long list of people Katz could honor: his martyred parents, brothers and sisters. The aunt who sheltered his family in Poland. The Hungarian woman who smuggled him under a pile of lumber. Members of the underground who gave him forged papers. The aunt and uncle who brought him to America. “They’re always with me,” he said. “In dreams, I see them.”

Katz’s wife and brother died recently, which got him thinking about how he’d like to be remembered. He wanted it to be a story his grandchildren would tell their children:

Grandpa Katz stepped up to the readers’ platform in synagogue on Memorial Day. He touched the Torah scroll with the corner of his prayer shawl and kissed it. Then he read from the Bible: “And ye shall teach them to your children, talking of them when thou sittest in thy house, and when thou walkest by the way.”