AMSTERDAM (JTA) — Gabriel Bach knew he was Jewish and that the Nazis were a serious threat, but at 13, leaving his new school and home in Amsterdam proved heartwrenching.

What if, the boy wondered, he could stay just a few more weeks to finish the academic year?

Bach would come to powerfully understand the answer to his query. About two decades later he was the prosecutor in the trial of Adolf Eichmann, the architect of the annihilation of European Jewry.

Fifty years ago this week, on May 31, Eichmann was executed in Jerusalem. Bach, 85, completed a series of lectures this month in Germany, Austria, the Netherlands, Belgium and the United States.

He was invited to Holland by the country’s watchdog on anti-Semitism, the Center of Information and Documentation on Israel, and the Arzi foundation for Dutch Israelis. The Israeli Embassy arranged for him to address 200 jurists and judges of the International Criminal Court at the Peace Palace in the Hague.

Bach even managed to swing by his old school in Amsterdam 72 years after leaving. During a visit to the Vossius Gymnasium, Bach recalled his truncated youth in the city.

That tragic chapter of Dutch history leapt back to him while reviewing yearbooks in the rector’s office. In Bach’s time at the school, one-third of the 400-member student body was Jewish. Fewer than 10 of them survived the war.

The rector, Jan van Muilekom, presented Bach with a small alabaster statue of a fox. Every graduate gets one, the rector explained to the judge and his wife, Ruth.

“You have not taken all the finals exams, but I’m pretty confident you would have passed,” he joked.

Now a Jerusalem resident, Bach had immigrated to the Netherlands in 1938 from Germany with his family. Two year later they were in Palestine — just weeks before the Nazis invaded Holland.

Bach remembered being in the car that would take the family to the train station and then out of Holland. Before it started to move, he leapt out and ran upstairs for his dog, Stompi.

“They had to tear him out of my arms,” Bach said in a rare expression of emotions outside his old home on Wagner Street. A savvy jurist, he mostly uses facts, figures and principles of jurisprudence in speaking about the past.

Ironically, Bach remembers feeling relieved after making it to Holland from Germany.

“We had been detained and frisked in Germany before crossing over to Holland. We then had to run to the train as it was pulling out,” he said. “A German SS officer kicked me in my behind as I was running. I was literally kicked out of Germany.”

On the Dutch side of the border, Bach recalled finally releasing his emotions.

“The Dutch customs official wasn’t even that nice, he was just correct. But to have someone in uniform address us as human beings … it moved me to tears almost,” he said.

Bach eventually became an Israeli Supreme Court justice. He is matter of fact when speaking about Eichmann, an SS Obersturmbannführer responsible for the murder of hundreds of thousands of Jews.

Eichmann escaped Europe after World War II, but Israel’s secret service, the Mossad, captured him in 1960 in Argentina. Eichmann was smuggled back to Israel, convicted of crimes against humanity and sentenced to death by hanging. His execution marks Israel’s only state-sanctioned death.

Bach, then a deputy state attorney, had led the prosecution’s investigation.

“I believe Eichmann became an expert in Jewish matters because he thought it would be beneficial for his career,” said Bach, the only member of the prosecution team who had contact with Eichmann. “When you murder thousands every day, you either go insane or you become an uncompromising idealist. Eichmann became obsessed with the idea of implementing the Holocaust.”

In reviewing tens of thousands of documents, Bach says he never once encountered “the slightest concession” on Eichmann’s part.

“I think it’s because doing so would have exposed him to himself as a common murderer,” Bach said. “That’s why he was so extremely fanatical in killing every last Jew.”

That fanaticism sometimes led to absurdity.

“I recall reading a document which showed how furious Eichmann was over a certain pogrom in which local Romanian militias killed Jews. Eichmann warned this killing of Jews ‘interfered with the statistical oversight’ of his task,” Bach said.

The only time Bach saw Eichmann unhinged was at a court screening of a documentary film about the Holocaust. The images were not what upset Eichmann; he was angry that he had not been allowed to wear his blue suit before being taken into the room.

Nowhere in occupied Western Europe was Eichmann’s Final Solution more thoroughly implemented than in the Netherlands. By 1945, more than 75 percent of Dutch Jewry had been murdered — in comparison to 20 percent in Italy, 26 percent in France and 50 percent in Belgium.

For Eichmann, the near total annihilation of Dutch Jewry appeared to have been a source of pride, even playing a decisive role in sealing his fate.

In 1956, while still living incognito in Argentina, Eichmann was interviewed by Wilhelmus Sassen, a pro-Nazi Dutch journalist. Eichmann’s family had hired Sassen to write Eichmann’s biography for posthumous publication.

Four years later Eichmann was captured, and Sassen sold a manuscript based on the interviews with Eichmann to Life magazine. The prosecution gained the notes from Life — complete with footnotes and corrections in Eichmann’s own handwriting.

In one interview, Eichmann told Sassen that the death trains leaving from Holland to Auschwitz were a “marvelous sight.”

The conversations were instrumental in discrediting Eichmann’s expression of remorse during the trial, in which he called the Holocaust “one of the greatest crimes in human history.” But armed with Sassen’s notes, the Israeli prosecution was able to show that just five years before the trial, Eichmann’s main regret was not having killed more Jews.

When Sassen asked if Eichmann sometimes felt sorry for his actions, Eichmann said, “Yes, I feel sorry that I wasn’t hard enough. That I wasn’t tough enough, that I didn’t fight these damn interventionists hard enough. And now you see the result: The creation of the State of Israel and the reemergence of that race there.”

Despite a childhood in the shadow of impending annihilation and a long submersion in the psyche of a mass murderer, Bach has not given up on what he called a “positive outlook” on the future.

“Holocaust denial and anti-Semitism exist,” he said. “Yet at the same time, the parliament of each state in Germany devotes a whole day every year to commemorating the Holocaust. I see a genuine determination to prevent things like that from reoccurring and I think that extreme pessimism isn’t very helpful.

“So they tell me, ‘Oh, Gabi, you always see the glass half full.’ They’re wrong: I actually see it as three-quarters full.”