The adventurer and artist John Castle, of mixed British and Prussian descent, was one of several foreigners commissioned by the Russian Empire to take part in the Orenburg Expedition which started in 1734. Its aims were to secure and encircle Bashkiria, to the north of present-day western Kazakhstan. The Russians planned to establish a line of forts, a trading base and centre for overseeing the Kazakhs at Orenburg at the junction of the Or and Ural (Jaik) rivers and to investigate the natural resources of the region. The Expedition attracted numerous merchants, surveyors and curious travellers. Castle volunteered to visit Khan Abulkhayir of the Lesser Kazakh Horde and to negotiate with him on behalf of the Russians. At the time Abulkhayir had been compelled, against the will of his people, to swear an oath of allegiance to Russia, and the situation with the Kazakhs remained volatile. Castle set off into virtually uncharted territory in the midst of chaos due to a major Bashkir rebellion prompted by the Orenburg Expedition. During his two-month journey he recorded his impressions of places, people and customs. Castle's diary describes this dangerous journey, subsequent events and his return to safety. It provides information on the tense political dynamics of the time, on the ethnography, geography and natural resources of Kazakhstan and on the difficult interactions between foreign members of the Expedition and Russian officials. The diary's rich ethnographic content, which includes first-hand observations of exorcism and divination rituals and the local administration of justice, gives clear and for its time extremely rare insights into the combined use of customary Kazakh steppe practices and Islam. It is a major historiographical source because it is written from the point of view of a foreigner and not a Russian. This book is the first English translation (by Sarah Tolley) and edition of John Castle's Journal von der AO 1736 aus Orenburg zu dem Abul Geier Chan der Kirgis-Kaysak Tartarichen Horda..., Riga 1784 (Journal of a Journey undertaken in AO 1736 from Orenburg to Abul Geier, Khan of the Kirgis Caysak Horde...). It reproduces the diary in full, with its glossary and 13 plates. These include unique illustrations of the Khan, his yurt and life on the steppe. An introduction provides the context of the Expedition, and footnotes accompany the text giving further clarifications and explanations.