The Mark 6 16 inch gun holds several distinctions relating to the United States' World War II combat history.
In the first instance, as the primary armament of USS Washington (BB-56) these guns were employed against the Imperial Japanese Navy's Kirishima (a much older and less powerful ship, armed with 8 x 14-inch guns and originally built as a battlecruiser during WWI) during the Naval battle of Guadalcanal; this has been cited by historians as the only instance in World War II in which one American battleship actually sank an enemy battleship. (While there was a battleship versus battleship engagement at Leyte Gulf, torpedoes rather than gunfire were largely regarded as being responsible for sinking the enemy battleships.) The Washington had the aid of a naval fire control computer—in this case the Ford Instrument Company Mark 8 Range Keeper analog computer used to direct the fire from the battleship's guns, taking into account several factors such as the speed of the targeted ship, the time it takes for a projectile to travel, and air resistance to the shells fired at a target. This gave the US Navy a major advantage in the Pacific War, as the Japanese did not develop radar or automated fire control to a comparable level (although they did have complex mechanical ballistics computers, which have been in use since World War I). Washington was able to track and fire at targets at a greater range and with increased accuracy, as was demonstrated in November 1942 when she engaged Kirishima at a range of 8,400 yards (7,700 m) at night. Using her nine 16"/45 caliber Mark 6 guns Washington fired 75 rounds of 16" AP shells and scored an incredible twenty heavy caliber hits that critically damaged the Kirishima, which eventually sunk. During the same battle, South Dakota also fired off several salvos from her 16"/45 guns before she had to withdraw for repairs to a faulty circuit breaker.
In the second instance, the battleship USS Massachusetts (BB-59) employed these 16"/45 caliber guns as her primary armament, and she is believed to have to fired the United States' first and last 16 inch shells of World War II; the first use occurring 8 November 1942 during the Naval Battle of Casablanca (shortly before the Naval battle of Guadalcanal), the last being 9 August 1945 off the coast of Hamamatsu, Japan. Furthermore, at Casablanca, this was the only time in the European theater that a fast battleship of the US Navy fired her guns in anger.