Software-defined networking (SDN) is an approach to computer networking that allows network administrators to manage network services through abstraction of higher-level functionality. This is done to achieve more centralized control and standardized interfaces. This is useful for military networks and is addressed in two articles in this Feature Topic on military communications The article by Wrona et al. gives an introduction to a variation of attribute-based access control, developed by the NATO Communications and Information Agency, referred to as content-based protection and release (CPR). The majority of the article then goes on to consider cross-layer enforcement of CPR policies in SDN, including a proof-ofconcept implementation. The topic of content-based security is highly relevant and likely of interest to many readers.