Today, interoperability is a challenge for the Swedish Armed Forces (SwAF) and will probably remain so considering the increased engagement in international operations. In order to facilitate interoperability, Sweden participates in the Multilateral Interoperability Programme (MIP). MIP is a collaboration between several nations and manages the development of a common information exchange data model for the C2 arena, named JC3IEDM. In order to enable delivery of required information to the C2 domain, it is necessary that systems are compliant with the JC3IEDM. This can be accomplished by integration of domain-specific ontologies with the JC3IEDM. This study explores the fundamentals of ontology integration, involving activities such as identification of suitable mappings between multiple ontologies, and automated translation of information between heterogeneous representation formats. Also, this study covers high level perspectives of ontology integration, including ontology management and tool support. The area of ontology integration has been explored in a multitude of research projects world-wide, and it has close connections with the area of database schema integration. However, more detailed studies and practical experiences are required in order to determine which methods and techniques are suitable for use within SWaF, in enabling semantic interoperability between various domains and the C2 arena (through the JC3IEDM).