Compare warships against their intended mission

How do you compare ships, including ships from different nations?

Assess each ship against its intended mission and role, then ask how well it performed them. Gun size, speed, range, and armour need that operational context.

A warship's intended mission gives its gun size, speed, range, and armour their context. Those figures can help a comparison, but they cannot establish how well the design met its navy's needs on their own. The insulation analogy makes this concrete: material suited to the walls can be a poor choice for the floor, while another house or application can change the choice again. Ships from different nations, and different ships within one navy, likewise need to be judged against the roles they were supposed to perform. Compare the intended task with what the ship actually did to assess whether the design worked well.