How are submarines used?

Answer 1

The modern military submarine is used in a number of roles. Note that the word submarine for the larger vessels that operate independently for extended periods. The smaller ones are more correctly called submersibles, and not submarines. The "true" submarines are generally divided into two types, with one being the larger, missile carrying one, and the other the smaller "attack" submarine that is designed as a hunter-killer of other submarines as well as surface ships.

The submarines (called boats by their crews) go on patrols. Boats with missiles basically "hide" in the ocean as a silent and "unfindable" deterrent. The attack boats patrol the oceans looking for other submarines so as to follow them around. This is the "meat and potatoes" of submarine operations, and took up most of the patrol time of the US and Russian submarines during the cold war. But there were some other operations that the boats were involved in.

Submarines were used to insert and pick up special forces groups on distant shores in hostile environments. They were also used to "sneak and peek" in places where we needed a closer look at surface ships, shore installations, or some electronics intelligence that we could gather by sticking an electronics mast up above the surface in a place where we couldn't get information in another way. The use of submarines to lay "electronics packages" that permit the US to tap into communications made on undersea cables is still mentioned now and then.

The uses of the modern military boats (submarines) to patrol the oceans, and to gain Intel and for other "hushed" projects is not something you'll read about in the paper or catch on the news -- at least if everything goes according to plan. The best policy, at least as far as the military and the submarines and their crews is concerned, is just to keep submarine operations (all of them) under wraps. This is largely what happens, too.