Following his receipt of his doctorate from Bonn in 1896, Karo travelled widely in the Mediterranean region, developing interests in Minoan civilisation, the Etruscans and on ancient biblical commentaries.

His outspoken German nationalism led to his dismissal from the DAI in 1916: he spent some time in the Ottoman Empire, where he worked to conserve cultural heritage and was linked with various efforts to appropriate ancient artefacts and bring them to Germany.

Karo's views made him unpopular with the Entente-backed government that ruled in Greece after the First World War, and he took an academic post at the University of Halle, which he held until 1930.

[1] In the same year, he began studying history, philosophy and archaeology at the University of Munich, under the art historian Heinrich Wölfflin and the philologists Wilhelm von Christ and Ludwig Traube.

[7] Following graduation in 1896, he moved to Rome, and spent the next six years on an extended study trip to Britain, France and the Mediterranean region, funded by his family wealth.

On the return journey, he visited Heraklion in Crete and met the British archaeologist Arthur Evans, the discoverer and excavator of the Minoan palace of Knossos.

In response, the DAI submitted a request to Theobald von Bethmann Hollweg, the chancellor of Germany, that Karo be granted the title of professor; this was approved.

[19] In 1911, Karo secured 10,000 marks[a] from Wilhelm towards the DAI's budget, which he justified to the Kaiser as an essential means of ensuring German "national prestige" through establishing parity with Greece's other foreign archaeological schools.

[22] He also took part in a tradition at the BSA, under the 1900–1906 directorate of Robert Carr Bosanquet, of comic lectures delivered on winter evenings: he attended in drag, while other members of the DAI came dressed as statues.

[26] Karo's work established the chronological relationships of the finds from Grave Circle A, and therefore allowed the beginning of the systematic study of Mycenaean material culture.

[14] During the First World War, Karo remained in Athens and worked to oppose the strong anti-German sentiment prevalent in the Greek press and popular opinion.

[34] Karo was rebuked by Ulrich von Wilamowitz-Moellendorff, considered among the most respected of Germany's classicists, and forced to leave Turkey; he departed for a holiday in Switzerland.

[41] The Greek state retained possession of the DAI's premises in Athens after the end of the war in November 1918: part of the building had been turned into a girls' school.

[44] Accordingly, in July 1920, Karo formally wrote to the directors of the DAI in Berlin, requesting to be dismissed from his post in Athens and complaining about the Greek government's treatment of him there.

She was then working as a secretary at Halle, and like Karo published articles in the Süddeutsche Monatshefte, a conservative magazine opposed to the Weimar government then ruling in Germany.

[12] However, his publications in his early years at Halle were dominated by political tracts, arguing against the Treaty of Versailles and denying claims of Germany's guilt for the start of the First World War.

[54] When the Nazis acquired control of Germany in 1933, they made an early priority of excluding those it deemed racially undesirable, including Jews and those married to or associated with them, from academic posts.

[60] From 22 May until 4 June, he worked with Carl Blegen, his long-time friend from the ASCSA, on the latter's excavations at Troy, and his former colleague Kurt Bittel arranged for Karo to be accommodated at the DAI to give a lecture on the finds from the site.

[73] On 12 July, Karo attended Wace's sixtieth birthday party at Mycenae, alongside several noted Greek and American archaeologists.

[83] The archaeologist Jack Davis has judged that Karo's presence ultimately had little impact upon his primary field of Aegean prehistory in the United States.

Unable to meet Marinatos in person, Karo sent him a letter containing eleven postcards, all showing an image of the Penn Museum and inscribed with a short greeting, signed pseudonymously "George Barbour".

He was also required to testify before an Enemy Alien Hearing Board in Cleveland on 18 April 1942 to avoid internment, something that he wrote would be "a death sentence" at his advanced age.

[95] He applied to be recognised as a victim of Nazi persecution, which would entitle him to government support as well as a resumption of his pension as an employee of the DAI: his application was accepted late in 1952 after Adenauer's personal intervention.

[100] In his memoirs, which he published in 1959, Karo chose only to discuss his life until the early 1930s, leaving out any mention of his relationship with the Nazi government, of his persecution in Germany, or of subsequent events.

[102] In 1921, Karo wrote a book criticising the terms of the Treaty of Versailles, denying claims of Germany's guilt for the start of the war, and attacking British imperialism.

[103] He was called to testify before a district court in Munich in spring 1922 on the question of German war guilt; this appearance gained him international recognition as one of the foremost experts on the subject.

[104] Karo's biographer Astrid Lindenlauf has written that he was "fond of the radical right", and that he was a member of the right-wing German Lecturers' Association (Deutschnationalen Dozentenbund) for several years, giving speeches at the group's annual meetings until 1929.

He also taught part-time at the Hochschule für nationale Politik in Berlin, which promulgated a nationalist, anti-democratic ideology; it was run by the historian Martin Spahn [de], later an early member of the Nazi party.

[105] During his leadership of the DAI during Nazi rule, Karo attempted to avoid recruiting so-called "non-Aryans" and wrote of his efforts to drive out Jewish archaeologists; however, he also favoured and supported the Jewish-born Wulf Schäfer, and recommended him for archaeological posts outside Germany.

[107] During a visit to Athens in September 1933, the German archaeologist Rudolf Herzog [de] recorded in his diary that Karo and his colleagues at the DAI approved of the recent rise of Adolf Hitler to power in Germany.