Arthur Koestler in the context of Order of the British Empire

In the 16th century, Nicolaus Copernicus proposed a major shift in the understanding of the cycle of the heavenly spheres. Driven by a desire for a more perfect (i.e. circular) description of the cosmos than the prevailing Ptolemaic model - which posited that the Sun circled a stationary Earth - Copernicus instead advanced a heliostatic system where a stationary Sun was located near, though not precisely at, the mathematical center of the heavens. In the 20th century, the science historian Thomas Kuhn characterized the "Copernican Revolution" as the first historical example of a paradigm shift in human knowledge. Both Arthur Koestler and David Wootton, on the other hand, have disagreed with Kuhn about how revolutionary Copernicus' work should be considered.

In the 16th century, Nicolaus Copernicus proposed a major shift in the understanding of the cycle of the heavenly spheres. Driven by a desire for a more perfect (i.e. circular) description of the cosmos than the prevailing Ptolemaic model - which posited that the Sun circled a stationary Earth - Copernicus instead advanced a heliostatic system where a stationary Sun was located near, though not precisely at, the mathematical center of the heavens. In the 20th century, the science historian Thomas Kuhn characterized the "Copernican Revolution" as the first historical example of a paradigm shift in human knowledge,. Both Arthur Koestler and David Wootton, on the other hand, have disagreed with Kuhn about how revolutionary Copernicus' work should be considered.

The Khazar hypothesis of Ashkenazi ancestry, often called the Khazar myth by its critics, is a largely abandoned historical hypothesis that postulated that Ashkenazi Jews were primarily, or to a large extent, descended from converts to Judaism among the Khazars, a multi-ethnic conglomerate of mostly Turkic peoples who formed a semi-nomadic khanate in and around the northern and central Caucasus and the Pontic–Caspian steppe in the late 6th century CE. It is still sometimes used in antisemitic conspiracy theories and in various anti-Zionist approaches. The hypothesis draws on medieval sources such as the Khazar Correspondence, according to which at some point in the 8th–9th centuries, a small number of Khazars were said by Judah Halevi and Abraham ibn Daud to have converted to Rabbinic Judaism. The hypothesis also postulates that after collapse of the Khazar empire, the Khazars fled to Eastern Europe and made up a large part of the Jews there. The scope of the conversion within the Khazar Khanate remains uncertain, but the evidence used to tie the subsequent Ashkenazi communities to the Khazars is meager and subject to conflicting interpretations.

Speculation that Europe's Jewish population originated among the Khazars has persisted for two centuries, from at least as early as 1808. In the late 19th century, Ernest Renan and other scholars speculated that the Ashkenazi Jews of Europe originated among refugees who had migrated from the collapsed Khazarian Khanate westward into Europe. Though intermittently evoked by several scholars since that time, the Khazar-Ashkenazi hypothesis came to the attention of a much wider public with the publication of Arthur Koestler's The Thirteenth Tribe in 1976. It has been revived recently by geneticist Eran Elhaik, who in 2013 conducted a study aiming to vindicate it.

The Information Research Department (IRD) was a secret Cold War propaganda department of the British Foreign Office, created to publish anti-communist propaganda, including black propaganda, provide support and information to anti-communist politicians, academics, and writers, and to use weaponised information, but also disinformation and "fake news", to attack not only its original targets but also certain socialists and anti-colonial movements. Soon after its creation, the IRD broke away from focusing solely on Soviet matters and began to publish pro-colonial propaganda intended to suppress pro-independence revolutions in Asia, Africa, Ireland, and the Middle East. The IRD was heavily involved in the publishing of books, newspapers, leaflets and journals, and even created publishing houses to act as propaganda fronts, such as Ampersand Limited. Operating for 29 years, the IRD is known as the longest-running covert government propaganda department in British history, the largest branch of the Foreign Office, and the first major anglophone propaganda offensive against the USSR since the end of World War II. By the 1970s, the IRD was performing military intelligence tasks for the British Military in Northern Ireland during The Troubles.

The IRD promoted works by many presumably anti-communist authors including George Orwell, Arthur Koestler, Bertrand Russell, and Robert Conquest.

Darkness at Noon (German: Sonnenfinsternis, lit. 'Solar eclipse') is a novel by Austrian-Hungarian-born novelist Arthur Koestler, first published in 1940. His best known work, it is the tale of Rubashov, an Old Bolshevik who is arrested, imprisoned, and tried for treason against the government that he had helped to create.

The novel is set between 1938 and 1940, after the Great Purge and Moscow show trials. Despite being based on real events, the novel does not name either Russia or the Soviets, and tends to use generic terms to describe people and organizations; for example, the Soviet government is referred to as "the Party" and Nazi Germany is referred to as "the Dictatorship". Joseph Stalin is represented by "Number One", a menacing dictator. The novel expresses the author's disillusionment with Bolshevism, Stalinism, and the ideology of the Communist Party of the Soviet Union at the outset of World War II.