 The port was subject to long range shelling by medium guns in Bardia , known to the Australians as " Bardia Bill " , and to Italian air attacks . Only one antiaircraft battery could be spared for Sallum . An air raid on Christmas Eve killed or wounded 60 New Zealanders and Cypriots . Without a proper warning network , interception was very difficult . However , on 26 December eight Gloster Gladiators of No. 3 Squadron RAAF sighted and attacked ten Savoia @-@ Marchetti SM.79 bombers escorted by 24 Fiat CR.42 biplane fighters over the Gulf of Sallum . The Australians claimed to have shot down two CR 42s , while three Gladiators were damaged . 
