A working upper-deck 4.5-inch mount before the war could have given Royal Navy destroyers much greater general-purpose firepower. The proposed counterfactual requires a late-1930s shielded mounting or turret; the more advanced postwar Daring-class installation would be out of place. Late-interwar doctrine already anticipated the new gun and the capabilities it would provide. When it failed to arrive, the Navy had to reconsider ship spacing and organization and return to a less efficient mixture of main guns and dedicated anti-aircraft weapons.
Notable Point · 1:02:33-1:04:08
A wartime 4.5-inch mount and the doctrine built around it
An earlier working 4.5-inch mount could have strengthened destroyer anti-aircraft fire, using a design plausible in the late 1930s.