In the network centric battlefield it is crucial that participating services can be discovered and used on an asneeded basis. Opportunistic service discovery in dynamic environments imposes some important requirements on the underlying service discovery system. In this paper, we discuss requirements for dynamic service discovery in the network centric battlefield, showing that current technologies for Web Service discovery are insufficient in this kind of environments. We then discuss design aspects of a service discovery architecture, advocating an autonomous federated registry topology and use of aliveness information. Finally, we briefly sketch some of the ingredients of a suitable service discovery infrastructure for a network centric battlefield.