Catalysis, milling, vacuum operation, and their interactions were studied as methods for increasing the rate of carbothermal reduction (CTR) of hard-burned and soft-burned MgO powders. For CTR at 1550 degrees C and 10 kPa, pellets made with soft-burned MgO reached 90% conversion in 30 min without milling and achieved the same conversion in 5 min with 120 min of milling. Crystallite attrition of soft-burned MgO was not observed, and the increased reactivity was attributed to mixing and aggregate attrition. Catalytic additives improved the reactivity in the CTR of hard-burned MgO but decreased the rate of CTR for soft-burned MgO. Additives were shown to catalyze the gas solid reaction pathway, and thermogravimetric analysis revealed that the rate of carbon oxidation by CO2 was approximately 2 orders of magnitude higher than that of MgO reduction by CO; thus, the latter reaction was rate-limiting to the gas solid reaction pathway.