This article is the first of two (Part 1 and Part 2) that shed light on militarychaplaincy in war-torn Ukraine. The first article introduces military chaplaincy inUkraine and sets the stage for Part 2, which focuses on the lessons learned by Ukrainianmilitary chaplains (MCs). The articles are based on interviews exploring the roles, practicesand insights of Ukrainian MCs during wartime, addressing a significant gap in theexisting research. Twelve male MCs participated in the study. Most of the participantshad served on the frontlines since the onset of the war in 2014, while a few joined morerecently, bringing a range of experiences, religious affiliations and branches of service(Army, Navy and Air Force). The interview data were analysed using thematic analysiswith an inductive approach. This first article presents the development, roles and tasksof military chaplaincy, covering the volunteer phase that began in 2014 and the professionalizationof military chaplaincy starting in 2022 and beyond. It also illustrateshow MCs operated in both non-combat and combat situations with their units. Thisresearch offers unique insights into the chaplaincy work of some of the most experiencedwartime MCs.