Military vehicle electrical power systems require quickly responding fault protection to prevent mission failure, vehicle damage, or personnel injury. The electromechanical contactors commonly used for HEV protection have slow response and limited cycle life, factors which could result in fuse activation and disabling of the vehicle, presenting a dangerous situation for the soldier. A protection technology not often considered is Solid State Circuit Breakers (SSCB), which have fast response and good reliability. Challenges of extremely high currents and voltages, high temperatures, and harsh conditions have prevented SSCBs from being effective in high power military vehicle electrical systems. Development of an SSCB for military vehicle power systems would increase electrical power system capacity and expand mission capability. The development of a 1.2 kV/200A Silicon-Carbide MOSFET based SSCB for combat HEVs is presented. The key innovation is packaging that minimizes losses, allows high temperature operation, and simplifies cooling requirements. We present results that show response times of less than 5 μs, operational ambient temperatures higher than 125°C, and a current density of 0.4 A/cm3. Our next-generation design will achieve a much greater current density of 12 A/cm3 by accommodating up to 2,000 A in a 10 in3 package. We present a compelling case that SSCBs overcome electromechanical contactor limitations while providing additional capacity and mission capability.