ships were also fitted with six submerged torpedo tubes, three on each broadside. They carried twelve to eighteen 6th Year Type torpedoes which had a warhead. They had three settings for range and speed: at , at , or at . In 1931–1933 the AA guns were replaced with eight 40-calibre Type 89 dual-purpose guns, fitted on both sides of the forward superstructures in four twin-gun mounts. When firing at surface targets, the guns had a range of ; they had a ceiling of at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute. Two twin-gun mounts for license-built Vickers two-pounder () light AA guns were also added. These guns had a maximum elevation of +80 degrees and a rate of fire of 200 rounds per minute. The pair of 14 cm guns on the upper deck were removed at this time. During the mid-1930s reconstruction, the torpedo tubes were removed and the Vickers two-pounders were replaced by twenty license-built Hotchkiss Type 96 light AA guns in 10 twin-gun mounts. This was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it a largely ineffective weapon. According to historian Mark Stille, the twin and triple mounts "lacked sufficient speed in train or elevation; the gun sights were unable to handle fast targets; the gun exhibited excessive vibration; the magazine was too small, and, finally, the gun produced excessive muzzle blast". These guns had an effective range of , and an effective ceiling of at an elevation of 85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines. In addition the forward pair of 14 cm guns in the forecastle were removed at this time and the maximum elevation of the remaining guns was increased to +30 degrees. Protection The Ise-class ships' waterline protective belt had a maximum thickness of of Vickers cemented armour amidships; below it was a strake of armour. The upper armoured deck consisted of two layers of high-tensile steel thick and the lower armoured deck also consisted of two layers of high-tensile steel, but only thick. The sides of this deck sloped downwards to meet the bottom of the lower strake