Tactical call signs are often adopted during an emergency, or during large public-service activities. Names like “Med Tent,” “Fire 1,” “Shelter 2,” and “Red Cross Staging” quickly identifies each function or location, and eliminates confusion when working with other agencies for which Amateur call signs are meaningless. They also help prevent confusion when several operators may take turns at a position.
The use of tactical call signs is a good idea, but it in no way relieves you of the obligation to identify your station under the FCC’s Rules for normal station identification. You must still give your FCC-assigned call sign at the end of your communication, and at least every 10 minutes during the contact [97.119]. This doesn’t mean that every ten-minutes everyone has to give their callsign – in an emergency net operation where tactical calls are being used, if it has been more than ten minutes since you last legally identified your station, you simply need to do so the next time you transmit.