This paper presents the development of a set of ontologies for use in messaging systems within military and emergency first responder command and control applications. These ontologies are used to annotate and subscribe to messages within a content delivery and service discovery middleware connecting sensors, services, and agents on the network. Ontologies serve an important role in this middleware in providing for flexible addressing and querying that increases the decoupling between senders and receivers afforded by the middleware. This is particularly important in the target applications, which feature heterogenous components and software versions spanning development organizations and deployment time. Discussed here are application uses, development methodology, evaluation criteria, and other notes on these ontologies and their creation. The goal of this paper is to provide useful input to others engaged in similar development efforts.