Why a damaged target could serve T-class doctrine

The T class was principally intended to wait for Japanese formations in Far Eastern waters rather than operate in Norwegian fjords. A ten-torpedo spread increased the chance of hitting something in a group before withdrawing. Sinking a target was valuable, but damage could impose a wider operational penalty by forcing escorts to slow, detach, or decide whether recovery was possible. Truant's attack on Karlsruhe demonstrated that logic in a very different theater.