The Kidnapping of Adolf Eichmann was a Mossad operation in Buenos Aires in May 1960 that brought a leading Nazi fugitive into Israeli custody and reshaped the hunt for Josef Mengele. The operation succeeded in capturing Eichmann, but its planned follow-up pursuit of Mengele failed: by the time Israeli agents searched for him, he had left Argentina. The episode joined an intelligence breakthrough to a missed opportunity, exposing how escape networks, national jurisdictions, and delays in sharing information could determine who was brought to justice.

Background: A refuge and a trail

After the war, Juan Perón’s government welcomed thousands of Nazis, Fascists, and collaborators to Argentina. Perón’s special Information Office and its escape networks connected intermediaries, officials, diplomats, and clergy in routes known as ratlines. By the late 1940s, Buenos Aires had become a center for exiled European fascists. The German and Dutch journalist Willem Sassen moved within this milieu, where he met Eichmann and other former Nazi officials. The social network that sheltered fugitives also offered investigators a place to search, but one in which trusted associates could warn one another and obscure identities.

The trail to Eichmann began with Lothar Hermann, a blind German Jewish refugee living in Argentina. His daughter had dated Nick Eichmann, who spoke admiringly of his father’s wartime record and regretted that Germany had not annihilated all the Jews. In 1957, Hermann wrote to Fritz Bauer, the chief public prosecutor in Hesse. Bauer chose to pass information quietly to Mossad rather than rely on intelligence agencies or the West German embassy in Buenos Aires, which he considered compromised by former Nazis. An initial Israeli inquiry proved inconclusive and stopped when Hermann demanded too much money. Bauer nevertheless believed him, and found a second source corroborating that Ricardo Klement was Adolf Eichmann. In December 1959, the decision was made to seize him.

The Eichmann investigation intersected with a separate pursuit. Isser Harel, Mossad’s director, wanted to add Mengele to his investigation board. He had only scattered information: Mengele was reportedly using the name Gregor and operating a furniture factory in central Buenos Aires. Harel planned to use the period after Eichmann’s scheduled capture on 11 May 1960 to find Mengele and bring him onto the plane taking Eichmann to Israel. Meanwhile, a West German arrest warrant for Mengele had been issued in February 1959, but the extradition request was entangled in delays and procedural obstacles. Mengele had obtained Paraguayan citizenship in November 1959, and the request’s progress through Argentine institutions gave him time to leave the country.

The capture and the failed second hunt

In early May 1960, Mossad commandos arrived in Buenos Aires. Harel carried Mengele’s coded file with him. On 11 May, as planned, the agents seized Eichmann. During his confinement, they questioned him about whether he knew Mengele, where Mengele was hiding, and what he looked like and did in Buenos Aires. Eichmann initially refused to betray his former comrade-in-arms, despite their differences and his contempt for him. Under continued questioning, he eventually supplied the address of a guesthouse in Vicente López, where Mengele’s wife and son had recently stayed.

The address did not lead the agents to Mengele. Harel sent two agents to the isolated villa, where the manageress said she knew no one named Gregor or Mengele. A postman recalled that a Mengele family had lived there but had disappeared weeks earlier without leaving a forwarding address. At the furniture factory, no one knew of a German called Gregor. Mengele was already in Paraguay. Harel considered raiding the guesthouse, convinced that Mengele might have returned, but his men warned that an assault could compromise the entire operation. The pursuit ran up against a basic intelligence problem: the information Eichmann provided was real, but it described a trail that had gone cold.

On 20 May, an El Al plane left Buenos Aires for Tel Aviv with Eichmann aboard, drugged and dressed as a member of the air crew. Harel told his men that Mengele would remain a target and that a new special unit would be created to track down Nazi fugitives. Eichmann’s capture therefore closed one operation while announcing another: the escape of Mengele did not end the pursuit, but made its failure unmistakable.

Repercussions and renewed pursuit

The capture sent shock waves through Nazi circles in South America. After David Ben-Gurion announced Eichmann’s capture to the Knesset, exiled war criminals feared that they might be kidnapped, arrested, or exposed next. Eichmann’s sons hurried to Sassen to organize a search for their father. Convinced that Jews were behind his disappearance, they discussed retaliatory action against the Israeli embassy or ambassador and searched Buenos Aires with help from the Tacuara Nationalist militia and Peronist Youth. Sassen was assigned to watch the airport. Their response showed how quickly one arrest could unsettle the networks that had helped fugitives live openly among sympathetic associates.

The consequences extended beyond the immediate search. Journalists converged on Buenos Aires, and the kidnapping humiliated Argentina while increasing pressure on West Germany to demonstrate that it would prosecute Nazi criminals. On 20 June 1960, a warrant was issued for Mengele’s arrest. The investigation nevertheless misidentified Lothar Hermann as the Auschwitz doctor, a reversal that underscored the risks of pursuing fugitives through incomplete information. Nazi groups in Buenos Aires began to fracture; Sassen’s friends suspected him of betraying Eichmann, and he sold recorded interviews with Eichmann to Life magazine and German and Dutch media before fleeing to Uruguay.

The capture also gave the pursuit of Mengele a durable public frame. In 1985, survivors testified at a mock trial at Yad Vashem in Jerusalem, while the Eichmann trial served as a precedent for presenting a fugitive Nazi before an international audience. The testimonies renewed pressure for Mengele’s arrest, and American, Israeli, and West German authorities coordinated their efforts. The kidnapping had shown that a fugitive could be brought to trial, but Mengele’s escape during the same operation revealed the limits of a pursuit divided across borders, delayed by bureaucracy, and opposed by networks of protection.