Destroyer forces do not have to use one homogeneous design. One class can emphasize a particular mission while another covers a different task, though each still needs enough flexibility to support the rest of the force. The difficult choice is the balance between specialized hulls and ships that can substitute for one another. Doctrine therefore lies partly in how the types are mixed, as well as in the qualities of each design.
Notable Point · 7:02-7:46
A destroyer force can divide missions among different designs
A navy may split destroyer work across specialized types, provided each design can cover enough secondary duties for the force to operate as a coherent whole.