The ability to rapidly mobilize the Marine Corps in times of crisis is a cornerstone of United States defense strategy. To mobilize rapidly, the marines need an efficient system for assigning officers to mobilization billets. The system we designed and built is based on a network optimization algorithm that works in conjunction with carefully designed and scrupulously maintained Marine Corps data bases. It takes less than 10 minutes on a 386-based personal computer to complete a mobilization involving 40,000 officers and 27,000 billets and to produce output suitable for generating orders to report via MAILGRAM. Prior to our work, the Marine Corps had a mainframe-based system that took two to four days to complete a mobilization. The new system is not only much faster than the old system, but it also produces significantly better assignments with respect to all measures of effectiveness considered.