The main guns were bored out to 320 mm Model 1934 naval gun and the center turret and the torpedo tubes were removed. All of the existing secondary armament and AA guns were replaced by a dozen 120 mm guns in six twin-gun turrets and eight Škoda 10 cm K10#OTO 100.2F47 History AA guns in twin turrets. In addition the ship was fitted with a dozen Breda Cannone-Mitragliera da 37/54 (Breda) light AA guns in six twin-gun mounts and twelve Breda M31 anti-aircraft machine guns, also in twin mounts. In 1940 the 13.2 mm machine guns were replaced by Breda Model 35 AA guns in twin mounts. "Giulio Cesare" received two more twin mounts as well as four additional 37 mm guns in twin mounts on the forecastle between the two turrets in 1941. The tetrapodal mast was replaced with a new forward conning tower, protected with thick armor. Atop the conning tower there was a fire-control director fitted with two large stereo-rangefinders, with a base length of .