The Norwegian campaign became a destroyer war because so many of its critical naval actions depended on these ships. British C, D, E, and F classes were broadly comparable to Germany's Type 1934 designs. The individual ships were similar enough for fleet size and replacement depth to become decisive differences. Germany had far fewer destroyers available, so losing ten at Narvik removed a large share of its effective force. Force structure made the same numerical loss far more damaging to one navy than the other.
Notable Point · 9:37-10:51
Norway as a destroyer war
The campaign's destroyer actions reveal why the loss of ten German destroyers at Narvik mattered so much to the naval balance.