Domestic defense companies in South Korea, including Kia, Hyundai Rotem, and Hanwha Ocean, are spearheading a shift towards eco-friendly technologies in the defense industry by incorporating hybrid engines and hydrogen-powered systems in tanks and submarines. Kia introduced the 'Hydrogen ATV Concept Car' that utilizes hydrogen fuel cells, offering enhanced performance and safety features for military applications. Hyundai Rotem is developing a hydrogen fuel cell-based 'Defense Drone' and a hybrid diesel-electric powertrain for the next-generation main battle tank 'K3,' focusing on improved operational capabilities and fuel efficiency. Hanwha Ocean's selection for the 'Energy Source System for Unmanned Submersibles' project highlights the development of a hydrogen fuel cell system for unmanned submersibles, aiming to enhance underwater endurance. Despite these advancements, challenges exist in the current hydrogen fuel supply system, emphasizing the importance of a gradual transition and infrastructure development. The ongoing integration of eco-friendly technologies in the defense industry aligns with global sustainability efforts, offering benefits such as reduced emissions and improved operational efficiency, shaping the future of defense towards a more sustainable and efficient infrastructure.