They are usually tasked with keeping a fixed high value choke points clear of mines, for example the approaches to military ports and harbours, especially in a cold war context those used by a nation's ballistic missile submarines.
They are usually tasked with keeping a fixed high value choke points clear of mines the approaches to military ports and harbours. This was for example. This was especially in a cold war context. Those used a cold war context by a nation's ballistic missile submarines.