Torpedoes and missiles: medium and guidance

Is a modern torpedo simply an underwater missile?

In some ways, but its underwater medium and usual wire-guided or fire-and-forget control arrangements still distinguish it.

The answer treats the medium through which the weapon moves as part of the distinction. Torpedoes are often wire-guided before transitioning to autonomous attack. Missiles commonly use a different control relationship and travel through air rather than water. The categories overlap conceptually, but medium and guidance architecture remain useful technical distinctions.