What do you do when the enemy deploys a jammer? One part of the military's broader cognitive radio strategy is/was radios that could avoid jamming by hopping to different parts of the spectrum.
Building a simple durable FHSS system isn't hard either, you could then effectively send a P25 data stream on top of it - the radio access channel and data stream are reasonably divorced in P25. Even then, its hard to build an effective broadband jammer - you simple move to another part in a say ~120MHz band.
