  This work investigates the potential of 5G and beyond sidelink (SL)
communication to support multi-hop tactical networks. We first provide a
technical and historical overview of 3GPP SL standardization activities, and
then consider applications to current problems of interest in tactical
networking. We consider a number of multi-hop routing techniques which are
expected to be of interest for SL-enabled multi-hop tactical networking and
examine open-source tools useful for network emulation. Finally, we discuss
relevant research directions which may be of interest for 5G SL-enabled
tactical communications, namely the integration of RF sensing and positioning,
as well as emerging machine learning tools such as federated and decentralized
learning, which may be of great interest for resource allocation and routing
problems that arise in tactical applications. We conclude by summarizing recent
developments in the 5G SL literature and provide guidelines for future
research.
