This study explores the resource mobilization of Ukrainian volunteer battalions during the 2014-2015 conflict, analysing how these non-state military actors strategically adapted without formal military infrastructure or state support to mobilize and maintain operational efficiency. The study highlights their innovative organizational tactics and resource utilization, emphasizing their ability to adapt and maintain combat effectiveness in challenging conditions. Utilizing the Resource Mobilization Theory (RMT), the research investigates the strategies these volunteer-battalions employed to mobilize resources, offering new insights into the role of non-state actors in modern warfare. This analysis addresses a gap in previous research which often uses narrow theoretical perspectives and consequently view these battalions as static rather than dynamic entities. The findings reveal that the effectiveness of the Ukrainian volunteer battalions was critically dependent on their ability to rapidly mobilize a wide array of resources. This was significantly enhanced by local and international networks, which facilitated resource acquisition and strategic operational planning. These networks also played a crucial role in legitimizing the battalions' activities and garnering broader societal support. Overall, this study contributes to the existing research by highlighting the pivotal role of resource mobilization in the establishing and maintaining of non-state military actors. It underscores the need for further research into the integration of social movement theories with military strategy to fully grasp the evolving nature of modern conflicts.