Why submarines change naval warfare into a three-dimensional contest

A submarine can exploit depth and thermal layers in ways that surface ships cannot, turning naval combat into overlapping contests above, on, and below the sea. Moving across a thermocline can place the boat outside the depth band where an opponent is concentrating its sonar search. Surface ships occupy the boundary between two three-dimensional battles, one involving aircraft overhead and another involving submarines below. This theoretical potential does not guarantee dependable combat effectiveness because every improvement must work against countermeasures developed to defeat it. The Tribal-class example shows how general-purpose destroyers could become effective submarine hunters instead of leaving the contest to specialized vessels alone.