This is a report on a study to improve electromagnetic compatibility in the field army through development of frequency-assignment practices. Detailed instruction is given in the fundamentals and use of the synthesis method of frequency assignment. Comparisons are made with the present ABM plan. Simplified templates for the determination of far-site assignment exclusions are presented. Assignment of frequencies to radio-relay and radio-net systems is illustrated in detail. In the theoretical sections previous work is expanded and consolidated where necessary to present a complete account of the years work. The general frequency-assignment problem is defined in terms of exclusions imposed by the physical nature of equipments and geographic locations. The problem is formalized through use of mathematical set theory, and solutions discussed. The basis for design of frequency groups which automatically satisfy the set theory expressions is established. Methods for replication of assignments and the combination of the replication scheme with the frequency-group method are covered. Optimization methods, and problems arising from intermodulation and adjacent-channel interference are considered.