The Tennessee class consisted of two dreadnought battleships— and —built for the United States Navy in the late 1910s, part of the "standard" series. The class was in most respects a repeat of the preceding , with the primary improvements being a significantly strengthened underwater protection system, and increased elevation of the main battery guns to allow them to fire at much greater ranges. They carried the same main battery of twelve guns in four triple turrets, and had the same top speed of . Both ships served in the Pacific Fleet for the duration of their careers, which included an extensive training program during the interwar period of the 1920s and 1930s.
Both ships were present in Battleship Row in Pearl Harbor when the Japanese attacked on 7 December 1941; California was torpedoed and sunk but Tennessee was only minimally damaged. California was refloated and both ships were heavily rebuilt between 1942 and 1944. The pair thereafter saw extensive service as bombardment vessels supporting the island-hopping campaign across the central Pacific. Tennessee took part in the Aleutian Islands campaign in mid-1943, the Gilbert and Marshall Islands campaign in late 1943 and early 1944, and the Mariana and Palau Islands campaign in mid-1944, by which time California had returned to the fleet as well.
They both took part in the Philippines campaign in late 1944, and were present at the Battle of Surigao Strait on 24 October, the final battleship engagement in history. A refit for Tennessee kept her from participating in the Battle of Lingayen Gulf in January 1945, where California was hit by a kamikaze, which in turn kept her from supporting Marine Corps troops during the Battle of Iwo Jima. Tennessee was heavily engaged in the fighting there and the subsequent Battle of Okinawa, where she, too, was hit by a kamikaze. The two ships spent the rest of the war patrolling the East China Sea until the official Japanese surrender in September. After briefly participating in the occupation of Japan, they were recalled to the United States and assigned to the Atlantic Reserve Fleet. They remained there until 1959, when they were sold for scrap.
Design
Design work on the Tennessee class, initially referred to as "Battleship 1916", began on 14 January 1915; the design staff used the preceding as a starting point. The General Board wanted to build a battleship that departed from the standard-type battleship series, particularly in terms of armor protection against the latest guns being fielded by European navies. They were opposed to simply developing the standard series, which incorporated relatively minor incremental improvements, but Secretary of the Navy, Josephus Daniels, overruled them and ordered that "Battleship 1916" would effectively repeat the New Mexico design with limited improvements.
At the same time that European navies had begun to adopt larger guns, they also began to develop longer-ranged torpedoes that could reach well into the expected battle distances of the day, . Therefore, the new ship's ability to resist underwater attack—naval mines in addition to torpedoes—became a chief concern of the designers. To ensure the ship could survive an underwater explosion, they decided to incorporate four torpedo bulkheads, which created four voids. Of these, the inner pair would be filled with either water or fuel oil, which would absorb the pressure and gas of the explosion. This system proved to be effective and it was used in many subsequent battleship designs.
The ships were authorized on 3 March 1915, while design work was still ongoing; tests on the torpedo bulkhead system were completed only in February 1916. In the meantime, work had already begun on the next class, initially designated "Battleship 1917", which became the . This class was essentially a repeat of the Tennessee design, the only major change was the adoption of larger guns in place of the guns the Tennessees carried. The turbo-electric drive propulsion system that was developed for the Colorados was retroactively applied to Tennessee and California in December 1915, before construction had begun on either vessel.
General characteristics and machinery
The Tennessee-class ships were long at the waterline, long overall, had a beam of , and a draft of . They displaced standard, and at full combat load. Under emergency conditions, additional fuel and ammunition could be stored, which significantly increased displacement to , which accordingly deepened draft to . The ships' hulls featured a pronounced clipper bow to handle high seas and reduce spray. A double bottom extended for the full length of the ships, and their hulls featured extensive compartmentalization to reduce the risk of uncontrollable flooding; below the waterline, the hull had 768 compartments and another 180 above the line.
The main deck, the highest deck that extended for the entire length of the ship, contained much of the living space for their crews, which included 57 officers and 1,026 enlisted men. As built, they were fitted with two lattice masts with spotting tops for the main battery. Steering was controlled by a single balanced rudder.
The ships were powered by turbo-electric drive. Eight oil-fired Babcock & Wilcox water-tube boilers generated steam that powered two Westinghouse turbo-electric generators that in turn provided power for four electric motors that drove four 3-bladed, screws. The turbines were in separate watertight compartments, arranged fore and aft, with four boilers apiece; each boiler had its own watertight boiler rooms, with two boilers on either side of the turbines. The motors were arranged in three rooms: a larger, central room for the two engines driving the inboard shafts, and one for each outboard shaft on either side. Each set of four boilers was ducted into its own funnel.
Their propulsion systems were rated at , generating a top speed of . On speed trials, Tennessee reached a maximum of from . Normal oil storage amounted to , but voids in the hull could be used to increase maximum emergency fuel capacity to . They had a cruising range of at a speed of , which fell to at normally; with full emergency oil their range more than doubled, to at 10 knots and at .
Armament
The ships were armed with a main battery of twelve /50 caliber Mark IV gunsA 50 caliber gun has a length 50 times its bore diameter. in four three-gun turrets, placed on the centerline in superfiring pairs forward and aft of the superstructure. Unlike earlier American battleships with triple turrets, these mounts allowed each barrel to elevate independently. Since Tennessee and California were laid down after the Battle of Jutland of mid-year 1916, which demonstrated the value of very long-range plunging fire, their main battery turrets were modified while still under construction to allow elevation to 30 degrees. This provided a maximum range of with the standard armor-piercing shell, which was fired with a muzzle velocity of . With the lighter high-capacity shell, the muzzle velocity increased to for a correspondingly greater range of . The guns suffered from excessive dispersion of shot, which was eventually discovered to have been caused by overly lengthy chambers, which allowed a gap between the shell and the propellant charges. The problem was eventually corrected with the Mark VII gun.
The secondary battery consisted of fourteen /51 caliber guns, ten of which were mounted in individual casemates clustered in the superstructure amidships at 01 deck level, one deck higher than the main deck. Six of the guns were arranged to fire forward and four were pointed aft. The remaining four guns were placed in open pivot mounts another deck higher at 02 level; two were placed abreast the conning tower and the others placed on either side of the funnels. Initially, the ships were to have been fitted with twenty-two of the guns, but experiences in the North Sea during World War I demonstrated that the additional guns, which would have been placed in the hull, would have been unusable in anything but calm seas. As a result, the casemates were plated over to prevent flooding. The guns were the Mark VIII type, which had a muzzle velocity of firing a shell.
The battleships carried four /50 caliber Mark X guns for anti-aircraft defense. These guns were located on the 02 deck, with two on either side of the boat cranes and the other two abreast of the mainmast. The guns fired a shell at a velocity of . They also carried a variety of other guns, including four 6-pounder saluting guns and a 3-inch Mark XI field gun and several machine guns for use by landing parties.
In addition to their gun armament, the Tennessee-class ships were also fitted with a pair of torpedo tubes, with one mounted submerged in the hull on each broadside. They were supplied with Bliss-Leavitt torpedoes of the Mark VII type; these carried a warhead and had a range of at a speed of .
Armor Their main armored belt was thick and was approximately wide, half of which was above the waterline. The thicker armor protected the ships' vitals, including the ammunition magazines and propulsion machinery spaces, extending from the forwardmost barbette to the aftmost barbette; the stern received lighter armor plating. Both ends of the main belt were capped by armored transverse bulkheads that were 13.5 in thick. The main armored deck was up to thick, and it was connected to the top of the main belt, running between the transverse armored bulkheads. A second armor deck that was thick was placed below the main deck; further aft, where it constituted the only horizontal protection, it increased in thickness to 5 in. On the ships' bows, the lower armor deck was increased to 3 in.
The main battery gun turrets had thick faces, thick sides, rears, and roofs; teak backing was used to cushion the structures from shell impacts. The turrets were mounted atop barbettes. Their conning towers had thick sides with thick roofs. The armored coamings for the funnel uptakes were 9 in thick.
Modifications
The Tennessees underwent a series of minor modifications to their secondary and anti-aircraft armament through the 1920s and 1930s. In 1922, Tennessee had the two 5-inch guns abreast the mainmast removed and four more 3-inch guns installed, two of which were placed where the 5-inch guns had been. The other two were placed behind the forward 5-inch mounts. All eight guns were removed in 1928 and replaced with eight 5-inch /25 caliber anti-aircraft guns. California was similarly rearmed during a refit in 1929–1930. Eight .50 caliber machine guns were added, six to the roofs of the spotting tops, two on the foremast and four on the mainmast. The other two guns were placed on pedestals on either side of the foremast. Tennessee had two of the 3-inch guns returned in 1940, placed on either side of the bridge wings.
Other changes included the installation of aircraft-handling equipment. California had an aircraft catapult installed on her aft superfiring turret and she received three Vought UO-1 seaplanes for reconnaissance and fire direction. Two years later, Tennessee was similarly modified, though her catapult was located on the fantail. In the early 1930s, she received a second catapult on her aft turret, and at some point California also had a catapult fitted to her fantail. During their 1943 reconstruction, the turret-mounted catapults were removed and both ships were fitted with just a catapult on the fantail.