During the Seven Years’ War (1756–63), the Russian ‘Expeditionary Army’ fought against Frederick the Great in Prussia. As well as regimental priests, an Orthodox ‘chief priest’ Ioann Bogaevsky from Ukraine was appointed, who was tasked with organizing the spiritual care of the army. Alongside him, Pastor Christian Täge, whose memoirs survive, was commissioned as Protestant chaplain. Based on their personal testimonies and unpublished archival materials, this article aims to reconstruct the organization of the military clergy in the Russian Imperial Army of the eighteenth century, taking into account its multi-ethnic and multi-confessional character. With this army including Protestants, Roman Catholics, Muslims, Buddhists, and even pagans in addition to Orthodox Christians, this article also considers what religious coexistence looked like in practice, shedding light on forms of military religiosity. Contrary to perceptions of the irreligiousness of the military, not only is their active participation in church sacraments noted, but also the persistent tension between religious and rational attitudes to warfare, which were clearly evident in conflicts about adherence to traditional practices of piety.