the USN re-adopted the intermediate battery, the British, Italian, Russian, French, and Japanese navies laid down intermediate-battery ships. Almost all of this later generation of intermediate-battery ships finished building after Dreadnought, and hence were obsolete before completion. Tertiary battery The pre-dreadnought's armament was completed by a tertiary battery of light, rapid-fire guns, of any calibre from 3-inch (76 mm) down to machine guns. Their role was to give short-range protection against torpedo boats, or to rake the deck and superstructure of a battleship. Torpedoes In addition to their gun armament, many pre-dreadnought battleships were armed with torpedoes, fired from fixed tubes located either just above or below the waterline. By the pre-dreadnought era the torpedo was typically in diameter and had an effective range of several thousand metres. However, it was virtually unknown for a battleship to score a hit with a torpedo. Range of combat During the ironclad age, the range of engagements increased; in the Sino-Japanese War of 1894–95 battles were fought at around 1 mile (1.5 km), while in the Battle of the Yellow Sea in 1904, the Russian and Japanese fleets fought at ranges of 3.5 miles (5.5 km). The increase in engagement range was due in part to the longer range of torpedoes, and in part to improved gunnery and fire control. In consequence, shipbuilders tended towards heavier secondary armament, of the same calibre that the "intermediate" battery had been; the Royal Navy's last pre-dreadnought class, the Lord Nelson class, carried ten 9.2-inch guns as secondary armament. Ships with a uniform, heavy secondary battery are often referred to as "semi-dreadnoughts". Protection Pre-dreadnought battleships carried a considerable weight of steel armour. Experience showed that rather than giving the ship uniform armour protection, it was best to concentrate armour over critical areas. The central section of the hull, which housed the boilers and engines, was protected by the main belt, which ran from just below the waterline to some distance above it. This "central citadel" was intended to protect the engines from even the most powerful shells. The main armament and the magazines were protected by projections of thick armour from the main belt. The beginning of the pre-dreadnought era was marked by a move from mounting the main armament in open barbettes to an all-enclosed, turret mounting. The main belt armour would normally taper to a lesser thickness along the side of the hull towards bow