In the late 1930s, he was close to the quasi-fascist dictatorship of Ioannis Metaxas, under whom he initiated legislation to restrict the roles of women in Greek archaeology, and he was later an enthusiastic supporter of the junta.

[17] He attended Halle on a scholarship, which he won in 1928 while serving as deputy to Stefanos Xanthoudidis [el], the senior ephor (archaeological inspector) of eastern Crete.

[20] Xanthoudidis died suddenly in 1929; Marinatos returned early from Halle to succeed him,[21][b] and was appointed as senior ephor of eastern Crete in March 1929.

His former teacher Karo, who had fled there from antisemitic persecution in Germany, asked Marinatos to forward on his behalf a series of postcards from Greece to various addresses in Nazi-occupied Europe.

Unsure of Karo's intentions, Marinatos gave the letters to his benefactor Elizabeth Humlin Hunt, in whose home he had been staying, to dispose of: she handed them to the Federal Bureau of Investigation.

[35] In May 1939, funded and assisted by Elizabeth Humlin Hunt, Marinatos discovered and excavated the battlefield of Thermopylae, the site of the last stand of the Spartans against the Persian Empire in 480 BCE.

[36] His excavation was widely reported in the Greek and foreign press, and played an important ideological role for the nationalist government of Ioannis Metaxas.

[39] Marinatos decided to excavate on Thera to test his hypothesis,[40] though the initially muted scholarly reaction to his ideas led him to reconsider his intention to begin this work in 1939, and it was subsequently further delayed by the Second World War.

[43] During the winter of 1940–1941, at which time Greece was under invasion from Italy, Marinatos collaborated with the British archaeologist Alan Wace to study the façade of the Treasury of Atreus, a late Bronze Age tholos tomb at Mycenae.

[46] His method of consulting local farmers and hunters about the location of surface finds allowed him to discover sites previously unknown to archaeology.

[7] Marinatos travelled to Italy, Germany and Austria on 1 May 1948, with the military rank of tagmatarchis (major),[47] to recover Greek antiquities looted during the Second World War.

[48] The trip lasted seventy-five days and was often frustrated by the non-cooperation of archaeologists, officials and soldiers from other Allied powers, but Marinatos succeeded in recovering the Aphrodite of Rhodes as well as objects looted from Knossos by the Nazi general Julius Ringel.

[52] Working in Messenia until 1966, he discovered over twenty archaeological sites,[7] including a monumental building with frescoes at Iklaina, a burial tumulus at Papoulia,[54] and the tholos tomb at Charakopeio.

[55] Marinatos briefly returned as director of the Archaeological Service in 1955, but was forced to resign in 1958 by the Prime Minister, Konstantinos Karamanlis,[56][f] and was succeeded by John Papadimitriou.

He was called back to Athens on official business and to commence the purchase of the land, and only able to return on 21 June, a week before the first season was due to conclude.

The excavation was supported by forty local pumice miners, and uncovered the first traces of frescoes, over a total of six days of work across the season.

[77] In the late 1920s, he was a supporter of Eleftherios Venizelos, a broadly liberal politician who had brought Greece into the First World War on the side of the Entente.

[80] The archaeological historian Andreas Vlachopoulos has judged that Marinatos's politics rarely influenced his work, but that he made "nationalist exaggerations in favour of the Greek race" during his excavations around Marathon.

[4] Marinatos was invited by the Nazi government of Germany to speak at the Sixth International Conference of Classical Archaeology, held in Berlin between 21 and 26 August 1939, as a representative of the Metaxas administration.

[86] Despite the ongoing Axis occupation of Greece, his comments were broadcast on national radio and garnered a strong reaction from the Greek public:[87] the historian and communist Yanis Kordatos denounced Marinatos in Rizospastis, the official newspaper of the Communist Party of Greece, and Karouzos and Yannis Miliadis wrote to the collaborationist Prime Minister, Konstantinos Logothetopoulos, criticising Marinatos's conduct.

[88] When the military junta known as the "Regime of the Colonels" seized power in 1967, they dismissed the director of the Archaeological Service, Ioannis Kontis, considering him politically unreliable.

Marinatos, described in a modern study as "utterly devoted" to the regime, was immediately reappointed to replace him,[61] under the title of "Inspector General of the Services of Archaeology and Restoration".

[42] Marinatos promoted his own supporters and oversaw the sacking of many Greek archaeologists, making particular efforts to remove his political opponents,[89] women – particularly Semni Karouzou, who was forced into exile in Italy and Germany – and adherents of progressive, non-traditional methodology.

[61][g] According to his daughter Nanno, he became disillusioned with politics in the last year of his life, particularly following the Turkish invasion of Cyprus in July 1974, and wrote in a letter that he was "a citizen of Minos and live[d] in 1500 BCE".

[70] In the later part of the twentieth century, more detailed analysis of the pottery from both Crete and Akrotiri indicated that the eruption occurred several generations before the end of Neopalatial civilisation, and the latter is now generally attributed to human causes.

During his third period as the head of the Archaeological Service, he was criticised for his abolition of the rigorous examination process by which new ephors were selected, and his approach to recruiting and promoting colleagues has been described as driven by cronyism and political manoeuvring.

[101] His colleague at the University of Athens, Nikolaos Kontoleon, wrote that Marinatos's administration "constituted an unprecedented attempt to curtail the scholarly activity of Greek archaeologists ... [and] exercised oppression [which] dismembered a whole service".

[102] According to the archaeological historians Dimitra Kokkinidou and Mariana Nikolaidou, his management had "a disastrous impact on future developments", as his methods and priorities were adapted by his successors after the return to democracy in 1974.

[7] The archaeologist Emily Vermeule, who excavated with Marinatos at Akrotiri, called him a "crack revolver shot, diplomat, astronomer, linguist, and portly wit".

[116] After the elder Marinatos's death, a bronze bust of him was erected in the garden of the Archaeological Museum of Chora, which holds many finds from his excavations in Messenia; one of the town's major streets is also named after him.