Diesel will continue to be the preferred energy source in the defense sector. In the future, it can be replaced by synthetic diesel. Many defense-related applications such as reconnaissance and command vehicles require solutions with low heat and noise signatures. Diesel fuel processor systems coupled with fuel cells offer promising low-maintenance solutions in this area. Fraunhofer IMM has developed a prototype of a diesel-based fuel cell system with a power output of 25 kW, which is the world's largest diesel based system currently available. The underlying reformer technology and system architecture will be explained, and the advantages over combustion engines will be highlighted.