 During the Second World War Berlin served in British Information Services in New York City (1940–2) and at the British Embassy in Washington, DC (1942–6), where he was responsible for drafting weekly reports on the American political scene. For four months in 1945–6 he visited the Soviet Union: his meetings there with surviving but persecuted members of the Russian intelligentsia, particularly the poets Anna Akhmatova and Boris Pasternak, reinforced his staunch opposition to Communism, and had a formative influence on his future intellectual agenda. After the war he returned to Oxford. Although he continued to teach and write on philosophy throughout the later 1940s and into the early 1950s, his interests had shifted to the history of ideas, particularly Russian ideas, Marxist and other socialist theories, and the Enlightenment and its critics. He also began to publish widely-read articles on contemporary political and cultural trends, political ideology, and the internal workings of the Soviet Union. In 1950, election to a research fellowship at All Souls allowed him to devote himself more fully to his historical, political and literary interests, which lay well outside the mainstream of philosophy as it was then practised and taught at Oxford. He was, however, one of the first of the founding generation of Oxford philosophers to make regular visits to American universities, and played an important part in spreading ‘Oxford philosophy’ to the USA.