He was Fellow and Tutor in Ancient History at New College, Oxford, from 1953 to 1977, where he taught scholars including Robin Lane Fox, Robert Parker and Nicholas Richardson.

His father, Ernest Henry de Ste Croix, who died when he was four, was an official in the Chinese Customs.

[2] His mother, Florence Annie (née MacGowan), was the daughter of a Protestant missionary: she was a firm believer in British Israelism.

[3] Ste Croix was educated at Clifton College, then an all-boys private school in Bristol, England.

[3] On 18 July 1941, he was commissioned in the Royal Air Force (RAF) as an acting pilot officer (on probation) with seniority from 12 June 1941.

[8] His commission was confirmed on 18 July 1942, and he was promoted to flying officer on 18 September 1942 with seniority in that rank from 12 August 1942.

[9] His job in the RAF was to interpret enemy radar signals to ascertain the location and destination of their aircraft.

[2] He served most of the War in the Middle East, stationed at Ismailia, Alexandria, and Cyrenaica:[2] in Egypt he had the opportunity to expand his knowledge of ancient languages.

[2] His main tutor was A. H. M. Jones, the college's new chair of the Ancient History, who remained an influencing figure on Ste.

[3] He also held a university lectureship, and gave lecture series in Greek History and topics such as slavery, finance, and food supply.

Croix—as an exponent of a Marxist epistemological approach—was frequently involved in debate with Sir Moses Finley, an advocate of Weberian societal analysis.

Croix is best known for his books The Origins of the Peloponnesian War (1972) and The Class Struggle in the Ancient Greek World: from the Archaic Age to the Arab Conquests (1981).

He was also a noted contributor on the issue of Christian persecution between the reigns of the Roman Emperors Trajan and Diocletian.

Croix's influential article The Character of the Athenian Empire, which first appeared in Historia: Zeitschrift für Alte Geschichte (1954, 3, pp.

The article was based on a paper The Alleged Unpopularity of the Athenian Empire delivered to the London Classical Association on 14 June 1950.

Croix instead interpreted it as a religious sanction (drawing an analogy with the Spartan demand, in response to the Megarian Decree and other Athenian policies, for Athens to expel some religiously-tainted citizens).

Croix maintained that the sanction was exercised not to hurt the Megarians, which it could not do because of the nature of trade and economics in the ancient world, but on religious grounds, which were felt to be genuine by the Athenians.

In his opinion, the book was "written to prove that Sparta bears almost sole responsibility for the outbreak of the Peloponnesian War".

The remaining chapters (VI Rome the Suzerain, VII The Class Struggle on the Ideological Plane, and VIII "The Decline and Fall" of the Roman Empire: an Explanation) focus primarily on Rome and put forth the thesis that it was the increasing dependence on slave labor and diminishment of what would be considered in a modern context the middle classes that was the actual cause of the collapse.