He was born as Yisrael Natanovich Halperin in 1911 in the city of Vitebsk, within the Pale of Settlement of the Russian Empire (modern-day Belarus), as the fourth child to a wealthy Jewish family.

His father, Rabbi Natan-Neta Halperin, was a graduate of the Lithuanian Volozhin Yeshiva, and his mother, Yocheved (née Levin), was a homemaker, the daughter of a wealthy local Jewish industrialist.

[3] His exact birthdate is unknown; it was recorded in his father's Talmud volume, but the book was lost due to the upheavals of the Russian Revolution and World War I.

The department’s role was internal security, and it dealt, among other things, with gathering intelligence on underground movements that did not accept the authority of the national institutions, such as the Irgun and Lehi, as well as on the activities of communists.

Shortly before the declaration of the State of Israel, Yisrael deployed an Arab agent on a mission to Amman to assess Jordan's intentions and whether they planned to go to war.

Isser Harel was the only individual in the history of the State of Israel to hold a position that consolidated both internal and external intelligence responsibilities, giving him unprecedented power.

In this context, Harel authorized an operation that later became a source of significant controversy: the surveillance and wiretapping of Mapam—a mainstream, Zionist leftist party with Marxist leanings, particularly due to the pro-Soviet stance of some of its members, such as Moshe Sneh.

Harel, worried about Sneh's influence and the pro-Soviet faction within Mapam, ordered a wiretap to be placed in the office of Meir Ya'ari, one of the party's leaders.

[10] Harel was also instrumental in the arrest of Aharon Cohen, one of the leaders of Mapam and a prominent figure in the Kibbutz Artzi movement, who was convicted of espionage in 1958 after meeting with a Soviet diplomat.

He became increasingly worried about the influence of Uri Avnery's weekly magazine, "HaOlam HaZeh", which was known for its anti-establishment stance and its harsh criticism of the Ben-Gurion government and the ruling Mapai party.

In response, Harel authorized the funding of a competing weekly magazine, "Rimon", which was designed to attract readers away from "HaOlam HaZeh" by offering a similar, sensational style of journalism.

This attempt to subvert a legitimate media outlet using state funds was widely criticized and is considered a low point in Harel's career.

This incident involved a group of German scientists who were assisting the Egyptian government in developing advanced rocket technology, which posed a significant threat to Israel.

Mossad agents in Europe attempted to discourage the scientists through a variety of means, including sending threatening letters and engaging in sabotage.

He believed that Ben-Gurion underestimated the danger and felt that the Prime Minister’s focus on maintaining positive relations with West Germany was misguided.

His resignation marked the end of an era in Israeli intelligence, as Harel had been the central figure in shaping the country's security services since their inception.

[13] Harel's departure from the intelligence community left a lasting legacy, but also set the stage for years of tension between him and his successors, particularly Meir Amit, who replaced him as head of the Mossad.

In 1957, members of the West German government provided Israel with information that Adolf Eichmann was hiding in Argentina under the name "Ricardo Klement".

Eichmann, as director of Department IV-B4 of Nazi Germany's Reich Security Main Office (RSHA) during the Second World War, had played a crucial role in the planning and execution of the so-called "Final Solution to the Jewish Question".

In 1959, he placed Harel in charge of the operation to locate, seize, and secretly extract Eichmann from Argentina, with the intention of returning him to Israel to stand trial.

In April 1960, Harel's team of agents arrived in Buenos Aires, and tracked Eichmann to a residence in the San Fernando neighborhood of the city.

[19] The Shin Bet also achieved a major success in 1961 with the exposure of Israel Beer, a prominent IDF officer and military commentator, as a Soviet spy.

[20] In the same year, another notable espionage case involved the arrest of Kurt Sitte, a professor of physics at the Technion, who was discovered to be spying for Czechoslovakia.

However, in 1965, amid the political turmoil surrounding the split within the ruling Mapai party, Harel was invited by Prime Minister Levi Eshkol to serve as a security advisor.

This move was seen as part of Eshkol’s effort to distance himself from the influence of David Ben-Gurion and his new political faction, Rafi, which included key figures like Shimon Peres and Moshe Dayan.

His books, such as The House on Garibaldi Street and The Great Deception, offered insights into the world of Israeli intelligence and earned him recognition as a leading authority on security issues.

His books, including The House on Garibaldi Street and Security and Democracy, became key texts for understanding Israel’s intelligence operations during its formative years.

[26] Harel's views on security, especially his staunch opposition to any form of accommodation with enemies of the state, influenced Israeli policy for years after his retirement.

His pioneering work in establishing and leading the Shin Bet and the Mossad shaped both organizations into formidable security agencies known for their effectiveness and reach.

Under his leadership, Israeli intelligence made significant strides, from the capture of Adolf Eichmann to the disruption of Soviet espionage activities in Israel.