Powertrain architecture is being reshaped by the electrification of heavy-duty military vehicles using hydrogen fuel cell technology, particularly in transmission systems. Unlike conventional internal combustion engines, hydrogen fuel cell electric vehicles (FCEVs) typically use single-speed or direct-drive configurations due to the high torque of electric motors. This paper examines the impact of hydrogen electrification on military vehicle transmissions, focusing on armored multi-role models such as the VBMT-LSR, Guarani, and Leopard 1A5 of the Brazilian Army. The study compares traditional gearboxes with alternative solutions optimized for fuel cells, analyzing the trade-offs in efficiency, durability, and operational adaptability. Additionally, it explores adaptations required for hydrogen internal combustion engines (H2-ICEs), considering their distinct characteristics and demands. The study employs a three-step validation methodology combining computational simulations, technical data analysis, and case studies of military vehicles. MATLAB and similar tools are used to assess efficiency, durability, and torque response under field conditions. Next, specifications from existing military vehicles in the Brazilian Army are analyzed to evaluate the feasibility of hydrogen powertrains compared to diesel-based solutions. Finally, the study examines international military projects that have already integrated hydrogen or electrification, such as GM SURUS and Rheinmetall Mission Master, drawing insights into the applicability of these concepts in the Brazilian military context. This research enhances the understanding of hydrogen-powered transmissions, contributing to the future development of more sustainable powertrain solutions and thus supporting the adaptation of military fleets to alternative energy sources and accelerating the adoption of hydrogen-based mobility in defense applications.