Second World War formations combined 20 mm Oerlikons and 40 mm Bofors with heavier weapons, including 4-inch, 4.5-inch and 5.25-inch guns, as well as fighter protection. Different calibres supplied overlapping defensive layers. In the Pacific, Japanese aircraft could circle beyond the expected reach of American 5-inch/38 guns, especially when the formation lacked carrier fighters to intercept them. British 5.25-inch guns could reach farther. Gunners could let the aircraft settle into that apparent safe distance before opening fire. Sea Harriers would supply another defensive layer beyond the ships' own weapons.
Notable Point · 31:34-33:28
Layered air defence and different gun ranges
Different gun ranges and fighter cover gave fleets overlapping defences, including a way to engage aircraft circling beyond American 5-inch/38 range.