Shipboard and shore guns in Taranto's defence

Why do accounts of Taranto list such a mixed set of Italian anti-aircraft calibres?

Because the defence included both shipboard guns and land-based weapons around the harbour, including older calibres pressed into the barrage.

Italian warships carried 100 mm and 90 mm anti-aircraft guns, with some older 76 mm weapons still present. Taranto's harbour defence also used land-based guns against the attacking aircraft, which helps explain the mixed calibres in ammunition records. The raiders faced a combined system of ships, shore positions, and locally available weapons rather than one uniform battery.