"O’Flynn has boldly ventured into little-known and relatively inaccessible regions that remain insufficiently explored by historians and missiologists. In his painstaking and at times over-detailed and long-winded narrative, he opens up vistas on missionary lives, travels and motives as broad and breathtaking as the Caucasus mountains around which the story revolves. He also leaves many helpful markers on the trail, challenging scholars to engage in greater depth with this neglected region. The book will be a fascinating resource for historians of the Persian and Russian empires, church historians and missiologists, as well as scholars engaged with Muslim/Jewish/Christian and inter-Church ecumenical relations." - Alison Ruth Kolosova, in: Journal of Ecclesiastical History Volume 70 (2019)"[This] is a useful book for understanding these missions that took place during the rise of Western hegemony over the course of the eighteenth and nineteenth centuries. It possesses a flowing narrative and is festooned with fascinating characters whose personalities and foibles are as central to understanding the missions as they were to their missionary efforts. It also integrates substantial previous research via its rich footnotes and extensive bibliography. This will enable future scholars to dig deeper into these missions, which certainly deserve monographs of their own. Therefore, O Flynn’s book provides fodder for future research that will further nuance our understanding of these missions on their own terms, in relation to one another, and where they fit into the larger imperialist trajectory of the West and its relationship with Russia and Persia in the long nineteenth century." – Robert John Clines, in: Journal of Jesuit Studies Volume 5.4 (2018)"Over more than a thousand pages, the author orders and paraphrases missionary correspondences, reports, travel accounts, memoirs and other sources that reflect the inner life of European mission projects in Iran and in Russia." – Michael Kemper, in: Die Welt des Islams 58.1 (2018)"What makes the reading interesting and adventurous, is that he [the author] also tells anecdotes, such as when a missionary lost and found his horse in the Caucasus, or walked on foot to Tblisi for 10 hours. He also completes his account with prosopographical as well as other necessary and detailed information. (...) An appendix consists of sources and literature, among them the manuscript sources from the various archives and Arabic and Persian Sources. (...) For me this scholarly apparatus might be the most valuable part of the book, as it gives insight into archival resources for further research." – Cornelia Soldat, in: Exchange Volume 47.4 (2018)"Dr. Flynn’s work, the product of a lifetime of totally dedicated scholarship, is by all accounts a monumental enterprise: not only in its sheer volume with over 1,000 pages of text, exploring around 25 different archives, and providing some 2500 printed sources listed in the bibliography; but also in its scope, aspiration, and achievement: it covers the entirety of the Western missionary enterprise in Iran and the Caucasus between the mid-18th and the mid-19th centuries, connecting the Safavid period to the Qajar era thorough the lesser known post-Safavid 18th century." – Association for Iranian Studies, Award News, in: AIS Newsletter 39.2 (2018)"[...] for the period prior to 1870, Thomas O'Flynn has written the definitive history of western missionaries in Iran and the Caucasus and for many years to come it will remain the authoritative text on the subject." – Willem Floor, MD, Bethesda