How should a navy balance the capability and cost of its patrol fleet?

How should a navy balance the capability and cost of its patrol fleet?

Start with the assigned mission: a modular convoy escort needs sonar, torpedoes, and short-range air defense; a principal national asset needs suitable combat equipment; a global-presence patrol ship can remain simpler while larger combatants cover the danger.

OPVs occupy the low end of a maritime-security fleet, which is distinct from the low tier of a war-fighting fleet. A Danish-style modular ship could receive towed-array sonar, torpedoes, and short-range surface-to-air missiles for convoy escort. Torpedoes would give it a response if a submarine came within close range, while missiles would add a layer of defense. A country relying on OPVs as its principal national-security assets has to choose equipment for that responsibility. A larger navy may use inexpensive patrol hulls for worldwide presence while reserving scarce combatants for theaters where fighting is expected.