Why light cruisers need a credible attack method

Could twelve lightly armed cruisers sensibly be sent against eight battlecruisers and destroyers?

Only an urgent mission, such as disrupting the Formosa invasion, or powerful torpedoes could justify it; light guns alone left the cruisers badly mismatched.

Sending twelve light cruisers against eight battlecruisers and destroyers initially appears difficult to justify. A large battery of long-range heavy torpedoes might give the cruisers a credible way to threaten capital ships. Five-and-a-half-inch guns alone do not explain the decision, especially against ships mounting multiple thirteen-and-a-half-inch weapons. Chat later clarifies that the opposing heavy force was invading Formosa, supplying the urgent operational reason for the light cruisers to fight. Without such an asymmetric armament or immediate purpose, the mismatch remains hard to explain.