By some distance the greatest New Testament theologian of the twentieth century, Bultmann's exceptional literary productivity in professional posts that coincided with the most difficult thirty-five years of German history followed by a long working retirement included streams of correspondence. Many of these have now been published in six large volumes. A seventh (with Käsemann) is overdue but available in the Nachlaß in the Tübingen University library and other items are in journals and elsewhere. The five large volumes already published by Mohr Siebeck are a fitting monument to a great man and a footnote to a not to be forgotten history. We are told who was sacked by the Nazis, and who were retired by the allies in 1945 for supporting the totalitarian state. A few theologians were imprisoned, but Bultmann got away with his criticisms of the regime and his support of Jewish colleagues and students.

Much of what is preserved has little interest now outside Germany, and is well summarised in Konrad Hammann's major biography (2008, 2012; English translation 2013). Details of holidays (with health spa) and domesticity reveal a happy family life (three daughters) despite their and his wife's health problems, hyper-inflation, inadequate housing, food and fuel shortages etc. Concerts, opera, theatre and wide reading of German and foreign literature and recent philosophy and politics, and notably the highest academic standards, reveal a high culture surviving in some (not all) élite circles in desperate times.

Far more space is devoted to academic politics, actual and impending vacancies, with sometimes penetrating and sometimes dismissive judgements about the calibre of present and possible future colleagues and many others. His verdicts on every lecture in all the many conferences he attended do not have the interest a century later that they no doubt had for their original recipients, but they reveal much of Bultmann's thinking about theology, and about the (Protestant) Church in Germany and a society suffering revolutionary change twice during his years in post.

The German system of faculties (sending three duly prioritised names to the government), and Bultmann's grasp of all departments of Protestant theology in Germany and strong views of its ecclesial responsibilities and also his support for former pupils in parishes and academic posts, yield a long list of academic clergy whose careers are summarised by the various editors in footnotes sometimes as long as the letters. Roman Catholic theology and biblical scholarship rarely feature. The latter was not often taken seriously by liberals before the 1960s, and Bultmann's most promising pupil Heinrich Schlier did not follow Erich Peterson to Rome until 1953, even then remaining moderately Protestant on Paul and conservatively Catholic only on Ephesians and Gnosticism (which some said led him astray, others into all truth). Unlike Barth and Bonhoeffer, Bultmann had little sense of the theological potential of the ecumenical movement.

Werner Zager edited in 2014 the correspondence with Bornkamm, all except ten notes from 1933 to Bultmann's death in 1976. He also edited in 2017 the correspondence with Harbsmeier and with Ernst Wolf, again from the fateful year 1933 and after. His introductions and gazetteer are reliable on the facts and tell us where to look for more useful information. Those two earlier Zager collections and half of this third one present a senior professor, settled in his theological convictions. They are therefore less interesting than the letters Bultmann wrote as his theology was taking its new shape in the early and mid-1920s, especially to von Soden. This latest volume and the early correspondence with Barth (oddly unlisted in this volume's bibliography) and the extensive correspondence with Gogarten, Bultmann's closest ally in systematic theology, provide some commentary on Bultmann's most important essay collection from 1924–33 (Faith and understanding I, English version 1969) and the lengthy academic reviews from 1908 to 1967, republished in 2002.

It is those glimpses of serious theological discussion from the golden age of New Testament theology which makes parts of these collections immensely stimulating and instructive, and of some relevance to the larger history of Western theology. The later letters throw further light on Bultmann's 1940s and ’50s controversy with conservatives over demythologising, and on the debates and disagreements with his former pupils in the 1950s and ’60s about the relevance of the historical Jesus for Christianity, Paul's and Johannine theology and early Catholicism in the New Testament. Vielhauer and Conzelmann were participants in all those debates and closer to Bultmann himself than the provocative partisan Ernst Käsemann. Both were young enough to escape Nazi persecution but badly injured in the war. The tone of Vielhauer's forty-seven letters is reverential. Bultmann's 118 to him include more from when the elderly scholar with eye problems needed help in updating his books for new editions. Conzelmann's four letters from 1954 to 1973 contain more independence. Bultmann's fourteen replies are therefore more like his always respectful correspondence with Barth (ed. Jaspert 1971, 1994; English 1981).

The letters to von Soden are on another level, and even more fascinating than the Barth and the Gogarten collections, despite von Soden's letters being lost. They had been close friends in Breslau from 1918 to 1920, and in 1924 Bultmann finally succeeded in securing his friend's move to Marburg where he died in 1945, having co-edited the revived Theologische Rundschau with Bultmann from 1929 to 1944, and been supported by Bultmann in his political and church-political opposition to the Nazi regime as a leader in the Confessing Church. Of the thirty-three letters from Bultmann to him (from 1920 to 1934) twenty-nine (116 pages – so some of the letters are long) are from their years apart (1920–4). These contain inside information on Bultmann's thinking written to a trusted friend who did not share his theological attraction to the new Barth-Gogarten movement nor to philosophies of human existence (Dilthey and Heidegger in particular). This is valuable because Bultmann's correspondence with Heidegger offers little, despite their friendship and collaboration, because as colleagues in Marburg from 1923 to 1928 they were in close personal contact as each informed and stimulated the other before their geographical and political parting.

Von Soden had been a pupil of Harnack and remained the solid Ritschlian liberal Protestant that Bultmann had been as a pupil of Herrmann, and more than half remained as he opened his thinking up to the changed cultural climate and allied himself with Barth and Gogarten while still trying to rejuvenate the older liberal theology through the ‘friends of Christliche Welt’, the Ritschlian flagship. He was over-optimistic about the common ground he found with the early Barth, but was willing to learn from his younger and more prophetic allies who were less respectful of their liberal Protestant past, later discredited by acquiescence in the ‘new Germany’. Both Bultmann and von Soden stood with Barth politically in the 1930s, but Bultmann's letters needed to say little about that as by then they had long been colleagues and neighbours. Those from 1920 to 1924 illuminate Bultmann's loyalty to and criticism of his older liberalism which he hoped to see develop with help from the dialectical theology. His letters, like his articles, show how, unlike Barth, he remained a devotee of Schleiermacher, F. C. Baur and their teacher Herrmann, and combined this with his leadership, as a New Testament scholar, of the history of religion(s) school in its second generation to create a new and distinctive philosophical and systematic theology whose weaknesses have long been recognised, and its strengths still under-estimated.

The theological content of what Bultmann wrote to his closest academic friend between 1920 and 1924 invites yet another monograph, but his commitment to the Lutheran Church at a time when ecclesial theology was as vital in Germany as it was in 1515–25 is illustrated here by his willingness to leave Marburg for a parish in his native Oldenburg if the university bureaucrats and an unhelpful dean could not solve his intolerable (and unhealthy) housing problem. A small matter in the larger scheme of things, but with resonance in Britain as some of the ablest students wonder whether they can afford an academic career.