Ethiopian Jews are being used as sex slaves in Saudi Arabia and Sudan
Twenty thousand had left their birthplace between 1977 and 1985, "motivated by an ancient dream", said Dr Gadi BenEzer.
They embarked on a "secret, illegal and highly traumatic exodus", he revealed at the Community Sherman Lecture at Manchester University.
Telling of the traumas of Ethiopian immigrants to Israel, Dr BenEzer explained that, like the Soviet Union, the Ethiopian Marxist regime regarded leaving one's country as a "confession of betrayal".
Paradoxically, the migrants made their way west to Sudanese refugee camps - in the opposite direction to Israel.
Their journey took them a long way on foot over unknown, dangerous mountainous territory, followed by an average stay of one to two years in refugee camps.
He described conditions as "extremely difficult".
Dr BenEzer, of Rishon Letzion's College of Management, said: "They experienced torture, bandit attacks, rape and hunger.
"Young girls were kidnapped from refugee camps.
Some are still sexual slaves today in Saudi Arabia and Sudan. A fifth of the group did not survive the journey.
"As many as 15 refugees a day died from epidemics in the Sudanese refugee camps," Dr BenEzer added.
The problems of the Ethiopian immigrants, he said, were compounded when their Jewish identity was called into question in Israel where they suffered prejudice and a lack of understanding.
Dr BenEzer recalled that in 1982 he began working as a clinincal psychologist and psychotherapist with Ethiopian immigrants in Israel.
As he won his clients' "trust and confidence", Dr BenEzer found that references to their journey formed a substantial part of their narrative accounts.
The immigrants felt the suffering they had encountered for the sake of their Jewish identity had not been recognised by the rabbinate, which had insisted on their symbolic conversion to Judaism.
One boy had told him: "The Israelis did not know what we went through. We were picked on."
Another said: "We suffered so much on the journey. Why did the rabbis treat us as non-Jews?"
In 1983, Dr BenEzer began a research project in which he interviewed 45 youngsters and young adults and more than 100 other Ethiopians.
He found their narratives contained themes of Jewish identity, suffering, bravery and inner-strength.
Jewish identity, he said, played a "crucial role in the decision to migrate. It was the fulfilment of an ancient, cross-generational dream".
One boy told how, when he would help his father plough his Ethiopian land, the father would explain it was not really their land. Their land was far away in Jerusalem.
Another recounted how his parents always blessed him that he should reach Zion.
The Ethiopians, he said, felt that their return to Israel would mean the return of a part to a whole. They were totally unprepared for problems of integration into Israeli society.
Dr BenEzer added: "They felt their journey had been directed by God. This gave them the strength to walk long journeys through mountainous terrain. They felt that God miraculously saved them."
Even on this tough journey, where they were besieged by robbers and wild animals, they had tried to maintain their customs and practices, keeping Shabbat, kashrut, Pesach and purity rites.
He said: "They thought they were reliving the Israeli exodus from bondage, that they had been called by God. They expected Israeli society to embrace them. But the opposite happened. The authenticity of their Jewish identity was not accepted, nor was their suffering.
"They were not seen as heroes but as helpless people saved by Israel. This had a tremendous psychological effect."
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