The Colorado-class battleships were a group of four United States Navy super-dreadnoughts, the last of its pre-Treaty battleships. Designed during World War I, their construction overlapped the end of that conflict and continued in its immediate aftermath. Though all four keels were laid, only three ships entered service: , , and . was over 75% completed when she was canceled under the terms of the Washington Naval Treaty in 1922. As such, the 16" gun Colorado-class ships were the last and most powerful battleships built by the U.S. Navy until the entered service on the eve of World War II.
The Colorados were the final group of the Standard-type battleships, designed to have similar speed and handling to simplify maneuvers with the line of battle. The cancelled which was to follow would have in several ways been a departure from this practice. Apart from an upgrade in striking power with their eight 16-inch guns, the Colorados were essentially repeats of the earlier . The Colorados were also the last American capital ships built with four main armament turrets and twin-mounted guns.
All three ships had extensive careers during World War II. Maryland and West Virginia were both present during the attack on Pearl Harbor on 7 December 1941. While Maryland escaped relatively unscathed, West Virginia was sunk in the shallow waters of the harbor but subsequently raised and repaired. All three ships served as naval gunfire support ships during numerous amphibious operations. Maryland and West Virginia were present at the last surface action between battleships, the Battle of Surigao Strait during the Battle of Leyte Gulf in October 1944. All three ships were placed into the reserve fleet after the end of the war and were scrapped by the late 1950s.
Design
The construction of battleships armed with 16-inch guns was envisioned by the General Board of the United States Navy and Bureau of Construction and Repair (C&R) as early as 1913, as the upgrade in gun caliber promised twice the kinetic energy of the 12-inch gun then in service and half again as much as the 14-inch gun then being introduced. The 14-inch gun dominated the design of battleships between 1913 and 1916, just as the 12-inch gun had dictated designs from 1908 to 1910. However, while the General Board approved the 16-inch gun as early as 1911, George von Lengerke Meyer, the Secretary of the Navy, felt that a move to the larger gun caliber would make capital ships still on the drawing board obsolete. For this reason, he restricted the Bureau of Ordnance to proceed no further than blueprints for the new gun as a hedge against foreign developments. He finally approved construction of this gun in October 1912 and the weapon was test-fired successfully in August 1914. This success, along with the unofficial news in several naval publications of 15- and 16-inch weapons being adopted by the United Kingdom, Italy, Germany and Japan, led the Board to consider cancelling the construction of the in favor of an up-gunned design. Such a move meant an increase of 8,000 tons per ship, twice as much as the jump from the s to the Pennsylvanias. Debate continued for the next three years. Each year, President Woodrow Wilson's Secretary of the Navy, Josephus Daniels, balked at the potential increase in cost and ordered instead that the design features of the Standard Class be continued, but eventually compromised with the 1917 design battleships by allowing their armament to be upgraded. However, this was the only substantial change permitted.
The design of the Colorado class was therefore adapted from the preceding ; other than the significant improvement of eight /45 caliber guns in four dual turrets taking the place of the Tennessee-class's twelve /50 caliber guns in four triple turrets, there was no major difference between the two designs. Likewise, the Tennessees were the results of modifications to the , which had been the most modern U.S. Navy capital ships to see service in World War I and had attracted the attention of British constructors both serving with and outside C&R. This similarity would carry over into the and es as the U.S. Navy further standardized its capital ship designs. This was partly the result of wartime experience, when over 250 destroyers and more than 450 submarine chasers had to be built quickly for service in the North Atlantic. The U.S. Navy had done this by a process almost akin to the assembly line, sticking to one basic design per class with a maximum amount of standardization and rationalization. Since the Naval Act of 1916 meant the imminent construction of 16 battleships and six battlecruisers, it was necessary to streamline production to save time and labor.
Nevertheless, while U.S. battleships were standardized as much as possible, design improvements were incorporated whenever practicable. Most of the changes in the Colorados were incorporated prior to any of their keels being laid. However, plans for the underwater protection—the ships' main defense against torpedoes and shells that fell short of the ship but traveled through the water to hit underneath the waterline—could not be worked out in time. The problem was that tests in caissons—experiments that would eventually prove that a series of compartments divided between being filled with liquid and being left empty would be a very effective defense against torpedoes—were not yet complete. In order to commence construction of the ships as soon as possible, proposals sent to shipbuilding corporations noted that if they were selected to build the ships, alterations to the design of the ships three months after their keels were laid must be allowed.
General characteristics
The Colorados were very similar overall to the Tennessees, with a overall length and a beam at the waterline of . They displaced at normal load and at deep load and had a draft of . As in the New Mexico and Tennessee classes, they were designed with a clipper bow to help keep the ships dryer in heavy seas, and also kept the secondary armament in the superstructure rather than in the upper hull (Pennsylvania and earlier classes), where the guns had proved to be excessively wet in heavy seas and thus were frequently unusable.
Propulsion Turbo-electric transmission, which had been used in the prior class, was retained here. Advantages included the ability for the turbines to run at optimum speed without regard to propeller speed, which led to greater fuel economy and range, and an easier sub-division of machinery, which increased the ships' ability to withstand torpedo hits. Each of the four propeller shafts was powered by a 5,424 kilowatt electric motor, fed by two two-phase turbo generators (General Electric for Maryland, Westinghouse for Colorado and West Virginia) rated at 5,000 volts). Eight oil-fired Babcock & Wilcox water-tube boilers, each in its individual compartment, provided steam for the generators. Altogether, the ships' power plant was rated at 28,900 electrical horsepower (EHP) to provide a flank speed of . With a maximum bunker capacity of 4570 tons, the Colorados range without refueling at sea was .
Armament
Main guns The Colorado class was armed with eight /45 caliber Mark 1 guns in 4 two-gun turrets on the centerline, placed in two superfiring pairs forward and aft of the superstructure, which fired a armor-piercing (AP) shell at a muzzle velocity of and a rate of about 1.5 rounds per minute to a range of at a maximum turret elevation of 30 degrees. Development of this weapon had begun in August 1913, using a bored-out and relined Mark 2 gun, with the promise of twice the muzzle energy of the /50 caliber Mark 7 guns and 50 percent more than the 14-inch /45 caliber weapon used on the New York-class battleships. After an initial proof firing in July 1914 and minor changes, the 16-inch Mark 1 was re-proved in May 1916 and production approved in January 1917. When the Colorados were modernized in the 1930s, these guns were rebuilt per standard navy practice and redesignated 16-inch/45 (40.6 cm) Mark 5 and Mark 8.
Secondary guns Fourteen /51 caliber Mark 15 guns were installed to defend against enemy destroyers. This was reduced to 12 in 1922. The Mark 15 fired a shell at a velocity of to a maximum range of at 20 degrees at a rate of seven rounds per minute and was extremely accurate, with a danger space longer than the range to the target for distances less than . As in the New Mexico and Tennessee classes, these were mounted in unarmored casemates on the main deck, one deck higher than in previous classes, to allow them to be manned in heavy weather if necessary.
Heavily damaged at Pearl Harbor, in 1942 West Virginia began a major reconstruction that saw her Mark 15 guns removed and replaced with sixteen /38 caliber Mark 12 dual-purpose guns in twin turrets. Urgently needed in the Pacific, Maryland and Colorado retained 8 of the prewar Mark 15s, in Colorado's case until the end of the war; the twin turrets planned and later installed were at that time in short supply, and it was only in May 1945 that Maryland would be refitted with 16 5in/38 in 8 twin mountings as in West Virginia. The Mark 12 fired a shell to a maximum range of and a maximum elevation of at an elevation of 45 degrees. They had a high rate of fire due to their being hand-loaded but power-rammed and their capability for easy loading at any angle of elevation. The introduction of proximity-fused anti-aircraft shells in 1943 made the 5 in/38 even more potent in this capacity.
Anti-aircraft guns
Four /23 caliber guns were mounted initially for anti-aircraft (AA) defense. This was increased to eight guns in 1922. These guns fired a shell at a muzzle velocity of to a maximum range of and ceiling of at an elevation of 45.3 degrees and a rate of between eight and nine rounds per minute. These weapons were replaced in 1928–1929 with the same number of /25 caliber guns, the first Navy gun designed specifically for AA use. They fired a shell at a muzzle velocity of at a rate of between 15 and 20 rounds per minute to a maximum range of at an elevation of 45 degrees and a ceiling of at a maximum elevation of 85 degrees. These weapons were supplemented with quadruple-mount (quad) 1.1-inch/75-caliber guns in 1937–1938.
In 1942, the air defense system on these ships was overhauled completely. In addition to their 5 in/25s, they carried sixteen Bofors 40 mm guns in quad mounts and up to thirty-two Oerlikon 20 mm cannons in single mounts. The quad 40 mm Bofors fired a shell at a rate of 120 rounds per minute per barrel nominal, 140 to 160 rounds per minute when horizontal (gravity assist), to a maximum range of at 45 degrees and a ceiling of . The 20 mm Oerlikons fired a shell at an average muzzle velocity of and a practical rate of between 250 and 320 rounds per minute to a maximum range of at 45 degrees and a ceiling of .
A second overhaul of AA defense was made between 1944 and 1945, as the Navy had found 20 mm shells too light to stop Japanese kamikaze planes; this plus the higher approach speeds of these planes made these manually-controlled guns obsolete. In their place, more quad 40 mm Bofors mounts were fitted. Maryland eventually carried 40 40 mm in 10 quad mountings and 36 20mm in 18 twin mountings (a different source has her with forty-four 40mm in 11 quad mounts and forty-four 20mm in 20 twin and 1 quad mountings.) Colorado had either 32 or 40 40mm in quad mountings but with 39 single, 8 twin and 1 quad 20mm. West Virginia carried forty 40 mm in quad mountings and 64 20 mm guns in 58 single, one twin and one quad mounting.
Armor and underwater protection