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The Colorado-class battleships were a class of three battleships built for the United States Navy after World War I. Four vessels were originally planned, but only three were actually completed The fourth ship, USS Washington (BB-48) was cancelled under the terms of the Washington Naval Disarmament Treaty of 1922 when she was near completion. As such, the Colorado-class ships were the last and most powerful battleships built by the US Navy until the North Carolina-class battleships were commissioned on the eve of World War II.


The Colorado-class battleships were the final group of Standard-type battleships to be designed, having similar speed and handling to simplify maneuvers with the line of battle. Apart from an upgrade in striking power to eight 16 inch guns, the ships were essentially repeats of the earlier Tennessee-class battleships. The Colorado-class was also the last battleship class to be built with four turrets using a dual mounted system. The change to larger guns was prompted by the Japan's Nagato-class battleships, which were also armed with eight 16 inch guns.

The construction of battleships armed with 16 inch guns was envisioned by the United States Navy, the General Board and the 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. This weapon was foremost the design of battleships between 1913 and 1916, just as the 14 inch gun had in designs from 1908 to 1910. However, while the General Board approved the 16 inch gun as early as 1911, the secretary of the navy felt that an upgrade to a new gun caliber might 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 successfully test fired in the August of 1914. This success, along with the unofficial news in several naval publications of 15 and 16 inch weapons being adopted by Britain, Italy, Germany and Japan, the Board considered abandoning construction of the Pennsylvania-class battleships in favor of an up gunned design. Such a move meant an increase in displacement of each ship by 8,000, twice as much as the increase in tonnage from the Nevada-class battleships to the Pennsylvania-class. 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 Standard Class be upheld. Daniels finally compromised with the 1917 design of battleship by allowing their armament to be upgraded. This, however, was the only notable change allowed.

The general design characteristics of the Colorado-class ships were therefore taken from the preceding Tennessee-class, other than the notable improvement of eight 16 inch (410 mm)/45 caliber in four dual turrets taking the place of the Tennessee-class's twelve 14 inch (360 mm)/50 caliber guns in four triple gun turrets, there was not a major difference between the two designs. Likewise, the Tennessee-class ships were the results of modifications to the New Mexico-class battleships, which had been the most modern design of battleship used by the United States Navy in World War I, and had attracted the attention of British constructors both serving within and without C&R. This similarity would carry over into the Lexington-class battle cruisers and South Dakota-class battleships as the US increasingly standardized it's capital ship designs. This was partially 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 US 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, this meant the imminent construction of 16 battleships and six battle cruisers, therefor making it was necessary to streamline production to save time and labor.

Nevertheless, while battleships of the United States were standardized as much as possible, design improvements were also incorporated whenever a design permitted. Most of the changes in the Tennessee-class ships 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, bids sent out to shipbuilding corporations noted that if they were selected to build the ships, an alteration to the design of the ships three months after their keels were laid must be allowed.


In general appearances and specifications, the Colorado-class battleships were extremely similar to the Tennessee-class, with a 190-meter-long overall length and a beam at the waterline of 30 meters, and a draught of 9.3 meters. They displaced 32,600 tons at normal load and 33,590 tons under deep load. Like the Tennessee-class, they were designed with a clipper bow to make the ships dryer in rough weather. One improvement over previous classes was the location of the secondary battery in the superstructure rather than the upper hull, where it had proved to be excessively wet.

The Colorado-class ships used a turbo-electric transmission for propulsion. Advantages of this system 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, which were General Electric for USS Maryland and Westinghouse for USS Colorado and USS 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, to provide a flank speed of 21 knots. With a maximum bunker capacity of 4,570 tons, the Colorado-class ships' range without refueling at sea was 10,000 nautical miles while maintaining a cruising speed of 10 knots (19 kph).

The Colorado-class was armed with eight 16 inch/45 caliber Mk. 1 guns, which fired a 2,100 pound (950 kg) armor piercing shell at a muzzle velocity of 790 meters per second and a rate of about 1.5 rounds per minute to a range of 31,400 meters at a maximum turret elevation of 30 degrees. Development of this weapon had begun in the August of 1913, using a bored-out and relined 13 inch Mk. 2 gun, with the promise of twice the muzzle velocity of the 12 inch/50 caliber gun and fifty percent more than the 14 inch/45 caliber gun used on the Nevada-class battleships. After an initial proof firing in July 1914, and minor changes, the 16 inch Mk. 1 gun was re-proved in May 1916 and production was approved in January 1917. When the Colorado-class were modernized in the 1930s, these guns were rebuilt per standard navy practice and re-designated 16 inch/45 caliber Mk. 5 and Mk. 8 guns.

The secondary battery comprised of fourteen 5 inch/51 caliber Mk. 15 guns, primarily to defend against enemy destroyers. This was reduced to twelve in 1922. The Mk. 15 fired a 23 kilogram shell at a velocity of 960 meters per second to a maximum range of 3,200 meters at 45 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 2,700 meters. As in the New Mexico-class and Tennessee'-class ships, 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.

In 1942, the Mk. 15 guns were replaced on USS West Virginia with sixteen 5 inch/38 caliber Mk. 12 dual-purpose guns in dual turrets. On USS Maryland and USS Colorado, ten of the Mk. 15 guns were retained and combined with eight 5 inch/38 caliber Mk. 12s in single mountings with protective shields. The dual turrets planned and later installed were at that time in short supply. The Mk. 12 fired a 55.18 pound (25.03 kg) shell to a maximum range of 15,903 meters at an elevation of 45 degrees. They had a high rate of fire due to them 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 inch/38 caliber gun even more potent in this capacity.

Four 3 inch/23 caliber guns were initially mounted for anti aircraft defense. This was increased to eight in 1922. These guns fired a 3-inch shell at a muzzle velocity of 500 meters per second to a maximum range of 8,000 meters and ceiling of 5,500 meters at an elevation of 45.3 degrees and a rate of between eight and nine rounds per minute. These weapons were replaced in 1928 and 29 with the same number of 5 inch/25 caliber guns, the first Navy gun designed specifically for anti aircraft use. They fired a 24 kilogram shell at a muzzle velocity of 657 meters per second at a rate of between 15 and 20 rounds per minute to a maximum range of 13,300 meters at an elevation of 45 degrees and a ceiling of 8,400 meters at a maximum elevation of 85 degrees. These guns were supplemented with eleven 28 mm guns in 1937 and 38.

In 1942, the air defense system on these ships was overhauled completely. In addition to her 5 inch/38 caliber guns, they carried sixteen Bofors AA guns in quad mounts and up to thirty-two Oerlikon AA guns in single mounts. The quad Bofors guns fired a 900 gram shell at a rate of 120 rounds per minute per barrel nominally, 140 to 160 rounds per minute when horizontal (gravity assist), to a maximum range of 10,180 meters at 45 degrees and a ceiling of 6,797 meters. The Oerlikon guns fired a 123 gram shell at an average muzzle velocity of 831 meters per second and a practical rate of between 250 and 320 rounds per minute to a maximum range of 4,400 meters at 45 degrees and a ceiling of 3,000 meters.

A second overhaul of anti aircraft 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 mounted Bofors guns were fitted. USS Maryland eventually carried forty quad Bofors guns and eighteen Oerlikons. USS Colorado's quad Bofors guns were increased to forty but she kept all her Oerlikon guns. USS West Virginia carried forty quad Bofors guns and fifty Oerlikon guns.

The "all or nothing" armor scheme introduced on the Nevada-class battleships was continued here, as throughout the Standard type warships, with armor suites virtually identical to the preceding Tennessee-class. The exception was an increase in belt armor near vital machinery to 16 inches to correspond with the increased main gun caliber. Otherwise, the minimum thickness along the belt remained 14 inches. Upper deck armor was 3.6 inches initially and was later increased to 4.1 inches. Lower deck armor ranged between 2.25 and 1.5 inches and was also presumably strengthened during conversion.

As with the Tennessee-class, the Colorado-class ships were modernized in the 1930s to improve their staying power. A new underwater protection scheme featured five compartments separated by armored bulkheads. 75 inches thick on either side of the ship. An outer empty one, three filled, and an empty inner one. In addition, the eight boilers were moved from their location in previous designs and placed in separate spaces to port and starboard of the turbo-electric power plant. This arrangement formed another line of defense, which would allow the ship to go underway if one or even an entire side of boilers was disabled. A consequence was a notable aesthetic difference between the New Mexico-class and Tennessee-class was the single large funnel of the former was replaced by two smaller funnels in the latter.

Other improvements taken from the Tennessee-class included an attempt to move the forward torpedo room away from the 16 inch gun magazines, as the room was considered vulnerable. Also, the design called for the use of external, rather than internal, belt armor so that a break in the continuity of the side structure would not take place, which would reduce drag in the water and any corresponding waste of power.


USS Colorado awaiting re-supplying off the Lingyian gulf in 1945.

With fiscal year 1917 appropriations, bids on the four Colorado-class battleships were opened on October 18, 1916, allthough USS Maryland's keel was laid on 2April 24, 1917, work on the other three ships did not commense until 1919 and 1920. With the cancellation of the first South Dakota-class battleships, the Colorado-class was the last US Navy battleships to enter service for nearly two decades. They were also the final US battleships to use twin gun turrets — the [[North Carolina-class battleship|North Carolina-class] and second South Dakota-class ships had nine 16 inch/45 caliber guns and the Iowa-class used nine 16 inch/50 caliber in three triple turrets.

Plans for modernization of the Tennessee-class and Colorado-class were made in October 1931, in part to take advantage of loopholes in the Washington Naval Disarmament Treaty of 1922. While reconstruction under this treaty was allowed only to increase protection from air and underwater attack, it could include improvements in fire control and increased elevation for main armament as these were not listed in the treaty. Also, any changes made inside the hull could be justified as meant to increase protection, even if the outcome meant increased speed or longer operational range, since the term "blister" had been specified to limit changes only outside the hull, such as main armor belt thickness and main gun caliber. Modifications to the secondary battery were also outside the purview of the Washington Treaty.

Included in initial plans was some protection against chemical shells which contained poisonous gas, although the General Board stated in the late 1920s that decontaminating a battleship hit with these shells would not be possible — the ship would have to be scuttled. Also, the deck armor was to be bolstered with 80 pounds (36 kg) of special treatment steel (STS), which would add 1,340 tons to the displacement of the ships. Among this was plans to thicken the armor on the tops of the main turrets, fire controls were to be improved with the latest technology, and new shells for the main guns were to be designed. Two, later four, 1.1/75 caliber guns were to be added, and all of the machinery in place would be removed in favor of newer equipment so that the ships would not lose any speed with the great increase in weight. Blisters were also to be installed to improve buoyancy but not to increase the ships' beams any greater than 32 meters (106 feet), so they could still use the Panama Canal when transferring from the Atlantic to the Pacific and vice verse. These improvements were estimated to cost about $15,000,000 per ship, totaling at $71,723,000. However, with the country in the throes of the Great Depression, not much money was available for Naval developments. Savings of $26,625,000 could be realized by reconditioning the propulsion machinery rather than replacing it, which would lower the ships' speed. Adding protection against chemical shells could be dropped, along with development of the new shells. Nevertheless, the cost saving elements of the later proposal were later dropped. The Navy asked the Secretary of the Navy to request money in the fiscal year 1933 to modernize the two classes from Congress, but the depression worsened. Although proposals for modifications were still made, plans were put on hold and eventually never carried out.

In the beginning of 1934, the Bureau of Construction and Repair proposed to fit "Big Five", as the two Tennessee-class and three Colorado—class ships had come to be known, with anti torpedo bulges so that the ships could benefit from increased buoyancy, because of, among other factors, the normal procedure of leaving port with the maximum amount of fuel possible on board, the five ships were quite overweight and rode low in the water. For example, in June 1935, USS Tennessee had a normal operating displacement of 38,800 tons, more than 2,000 tons above the maximum emergency load her original design called for. This made her draft higher, meaning that the ship's waterline was down 1.6 meters (5 feet 4 inches). Construction and Repair called for a bulge on the Colorado-class ships that would displace about 2,000 tons and raise the ships' draft by 510 mm. Installing these would be a year's worth of work, with each ship spending six months of that in a dry dock. The first month docked so that the hull shape could be determined, the next six sailing while the bulge was built, and the last five back in the dock so it could be added to the ship.

Three years later, in 1937, the various Navy bureaus held a joint meeting to discuss a possible partial modernization of the Tennessee-class and Colorado-class. They were much different than the changes proposed in 1933. There were no provisions for extra deck armor, but many additions and replacements. To gain space for newer fire control systems, the ships were to be reboilered. The main and secondary battery fire controls were to be replaced, including new rangefinders and plotting room instruments for the main battery, while new Mk. 33 anti-aircraft fire control directors were planned. The mainmast and Browning M2HB machine guns would be removed, and studies of the feasibility of a torpedo bulge, the addition of which Construction and Repair believed to be paramount, which would increase the beam to 33 meters (108 feet) and displacement to 40,200 tons. Varying plans for these were complete by October 1938. None was a full reconstruction. Costs ranged from $8,000,000 to $38,000,000 per ship. However, as the money for the improvements would lessen the amount available for new battleship construction, and these would be better than even reconstructed old battleship, the Secretary of the Navy rejected these plans in November. Congress did appropriate $6,600,000 in 1939 for some of these improvements, including the torpedo bulges.

With the beginning of World War II in Europe, the US Navy began to apply lessons learned by the British to there ships. The King Board of 1940–1941 proposed sweeping changes to the secondary armament of the battleships to increase their defense against air attacks. These included the removal of all 5 inch (130 mm)/25 caliber guns and 5 inch/51 caliber guns in favor of the dual purpose 5 inch/38 caliber, the addition of six quad mounted 1.1 inch (28 mm) guns, and the cutting away of superstructure to clear arcs of fire for the new anti aircraft weapons. An ultimate secondary battery of sixteen 5 inch/38 caliber fixed on dual mounts, sixteen Bofors AA guns in quad mounts and eight single mounted Oerlikon AA guns was called for by the board in 1941, although they were not certain the ships could handle the added weight and it would take a large amount of time in dry dock for these modifications to take place. With these concerns, an intermidiate measure of four 1.1 inch guns was proposed by the board. However, the gun was not being produced in any great number very quickly, so a second interim solution was implemented. By June 1941, all the United State's battleships, except for USS Arizona and USS Nevada, were armed with several 3 inch (76 mm)/50 caliber guns. These were replaced on the three battleships in the Atlantic by the 1.1 inch gun by November. They received them first because they were closer to a war zone.

As these modifications were carried out on the battleships, much additional weight was added onto the already overweight ships, forcing torpedo bulges to be added so that a decent freeboard could be maintained. These would cost $750,000 and around three or four months in a dry dock. The King Board suggested that the deck armor be bolstered and 5 inch/38 caliber dual purpose guns be added, but the Chief of Naval Operations decreed that any major changes such as these had to wait due to the wars raging around the world at the time. The addition of bulges, however, was approved for the "Big Five", with each ship spending three months in dry dock at the Puget Sound Naval Yard. USS Maryland would be first, she was in dry dock from February 17 to May 20, 1941, followed by USS West Virginia, from May 10 to August 8, and USS Colorado (BB-45)|USS Colorado]] was the last Colorado-class ship to be equipped with bulges, from July 28 to October 28. The estimates for how long the addition of bulges would take were too low. Puget Sound believed that they could complete work on USS Maryland in 123 calendar days, about four months, if the work would be given a priority equal to that of the refit on the aircraft carrier USS Saratoga.

Only two of the ships had bulges added to them through this program, USS Maryland was completed on August 1, 1941, and USS Colorado on February 26, 1942. The attack on Pearl Harbor on December 31, 1941, interrupted the refits intended for USS West Virginia. The surprise strike did not touch USS Colorado, which was at Puget Sound, and did not hurt USS Maryland very badly. However, USS West Virginia was severely damaged and left partially sunk in grave needed of a major refit.

Little to no major modifications were made to the two active Colorado-class ships in the opening months of the United States's entry into the War. All of the battleships in the US Pacific Fleet had a constant order to be ready to sail within 48 hours in case of a Japanese attempt to invade Hawaii or the West Coast, and could not be spared for any major yard work. USS Colorado was hurried through the rest of her refit with the addition of essential items like radar, splinter protection, fourteen more Oerlikon AA guns and four 1.1 inch light anti aircraft guns. USS Maryland received a similar treatment later, the only difference being sixteen Oerlikon guns and no 1.1 inch guns. Although tower masts were constructed for USS Colorado and USS Maryland and a majority of the old cage masts were cut down by the ships' crews in the beginning of 1942, the ships could not be spared for the time it would take to install the new masts. The tower masts were placed into storage and not used until early 1944.

Colorado and Maryland were greatly needed in the war zone, and as such did not undergo a major refit until 1944, although minor additions and removals, mainly to the anti aircraft weaponry, were made in between operations. Throughout the War, both ships saw their anti aircraft battery changed constantly. Beginning in 1942, they carried eight 5 inch/25 caliber guns, four quad mounted 1.1 inch guns, a greatly varying number of Oerlikon AA guns, and eight Browning M2HB 12.7 mm machine guns. In June 1942, USS Colorado had fourteen Oerlikon guns, and just five months later, this was upped to twenty-two, with thirty-six temporarily approved for a later time. By February 1943, both Colorado and Maryland had two more quad 1.1 inch guns added, bringing their total to six, and a total of forty-eight Oerlikon guns. A month later she was given an additional ten 12.7 mm machine guns. November 1943 saw the removal of two of the single-purpose 5 inch/51 caliber, the six quad 1.1 inch guns, and a number of Oerlikon guns, six in USS Colorado and eight in USS Maryland, in favor of thirty-two Bofors AA guns in six quad and two dual mounts.

Both ships finally underwent major refits in 1944. Here the remaining cage masts were taken off in favor of the tower masts, the two dual 40 mm replaced by quad mounts, a quad mount of Oerlikon AA guns added, and a new radar was equipped. Although more extensive refits were proposed by Admiral Ernest J. King, including the addition of eight dual 5 inch/38 caliber guns, more advanced fire control systems, and a second protective deck plating, the Bureau of Ships, after demonstrating what would have to be removed as compensation for the weight added for King's previous proposals, counter proposed that a smaller reconstruction, like the ones given to the New Mexico-class battleships, would be more desirable. However, no action was taken until USS Maryland was struck by a kamikaze aircraft. While undergoing repair, eight dual 5 inch/38 caliber guns were added, but nothing else. Her conning tower was removed and replaced by a 50-pound (23 kg) special-treated steel structure to balance the additional weight of the 5 inch guns.

All three ships had extensive careers during World War II. The three ships were put into the reserve fleet after the end of the war, where they remained until finally being scrapped in the late 1950s.

Ships in class

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