What is a Polaris submarine missile patrol?

Ballistic Missile Submarine patrols are meant to provide the sea-based leg of the nation's strategic nuclear defense triad (sea, air, and land based strike/defense capability).

FBM submarines are given a designated area to patrol, that puts them within range of their targets should an order ever come. They avoid all contact with ships or other submarines, and do not respond via radio unless in emergencies or specifically instructed to by their respective commands.

FBM's have 2 crews that rotate every 3 months. One month is spent for transfer and refit of the boat, and the other 2 months are spent for transit and actual patrol time.