Wyoming - class battleship The " Wyoming " - class battleship was the fourth series of two dreadnought battleship s built for the United States Navy . The class comprised two ships : and . At the time of the design of this pair of dreadnoughts , not a single one of the previous designs had yet gone to sea . While somewhat larger than their predecessors they retained all the features that were common to American battleships to date , with centerline turrets , low freeboard , long service ranges , and very thick side armor . They were also the last U . S . capital ship s armed with 12 inch ( 305 mm ) guns ; the battlecruisers which would follow in World War II were classified by the navy as " large cruisers " , despite having 12 " guns . The two ships served during both World War I and World War II . In the First World War , both ships were assigned to the 6th Battle Squadron of the British Grand Fleet , and saw limited action in the North Sea from 1917 to 1918 . " Wyoming " and " Arkansas " were both rebuilt in the mid - 1920s , as was the case for all of the American battleships of the era . Due to the Washington Naval Treaty , " Wyoming " was reduced to a training ship after 1931 , while " Arkansas " saw convoy escort duty during World War II . She also conducted shore bombardment in support of the invasion of Normandy , as well as in Southern France during Operation Dragoon , both of which were conducted in mid - 1944 . She was then transferred to the Pacific theater , where she bombarded Iwo Jima and Okinawa during the amphibious invasion s of those islands . Both ships were struck from the Navy list after the end of the war ; " Wyoming " was scrapped in 1947 , while " Arkansas " was expended as a target during the Operation Crossroads nuclear weapon test s in 1946 . Design . The requirements for this class arose from the very general requirements of the 1908 Newport Conference . This design marked the end of the Board on Construction and the rise of the General Board in U . S . ship design . The class marked a significant growth over its predecessor — the — of some 20 % in size . The " Wyoming " class was the fourth class of 11 separate designs begun from 1906 to 1919 ; some 29 battleships and 6 battlecruisers would be laid down during this period , though seven of the battleships and all six of the battlecruiser s would be cancelled due to the Washington Naval Treaty in the early 1920s . All except the would be designs and would range in weight from 16 , 000 to 42 , 000 tons . At this time , no U . S . dreadnought class battleship had yet hit the water as all were either at some stage of building or in design . Virtually the entire U . S . Navy battle line was being designed by drawing on experience from pre - dreadnought designs , or from observation of foreign battleship design . The Newport Conference established a general consensus among leaders that U . S . Navy ships should carry larger batteries in response to the increasing caliber of battleships in other countries , notably the BL 13 . 5 inch Mk V naval gun which had been introduced by the Royal Navy ' s " Orion " - class battleship . There was debate at the time as to whether the " Florida " - class battleship s , laid down in 1909 , should carry heavier armament than the 12 inch ( 305 mm ) Mark 5 gun . On 26 August 1908 , Secretary of the Navy Victor H . Metcalf authorized drawings for ships with eight or ten 14 inch ( 356 mm ) guns and heavy armor , with the first ships anticipated for delivery in June 1911 . President Theodore Roosevelt took personal interest in the design , favoring an eight - gun ship with a displacement of over a 10 - gun ship with a displacement of . Ultimately , on 30 March 1909 , U . S . Congress approved the construction of two " Design 601 " battleships with six twin 12 inch ( 305 mm ) turrets , which the General Board had selected over two 14 inch ( 356 mm ) designs in 1909 . Armament . Main guns . The " Wyoming " s were armed with twelve 12 " / 50 caliber Mark 7 gun s ( 305 mm ) in six twin turrets , all on the centerline and with the superfiring pattern repeated with the midship pair of turrets . The Mark 7 probably had a longer continuous active service life in the U . S . Navy than any other large caliber weapon ; it would first go to sea aboard USS " Wyoming " in 1912 and remain in service until USS " Arkansas " was sunk during the Bikini test s in 1946 . This weapon was only slightly more powerful than the preceding 12 " / 45 Mark 5 ( 305 mm ) gun . It fired an armor piercing ( AP ) shell at a muzzle velocity of and a rate of between two and three rounds per minute to a range of at a maximum elevation of 14 . 7 degrees . As in the " Delaware " and " Florida " classes , the midships turrets in both this and the following s proved problematic ; the turrets and magazines were both located near the boiler spaces with high pressure steam piping surrounding the magazines . This produced a marked temperature difference in the powder charges and contributed to excessive dispersions in the pattern of shell fall from the two classes . Attempts to cool the 12 " midship magazines were only moderately successful . The General Board estimated that battle ranges for the main armament would be 8 , 000 to . Secondary armament . Twenty - one 5 in / 51 cal ( 127 mm ) guns were fitted initially on " Arkansas " and " Wyoming " . Sixteen of these were mounted in individual casemates below the main deck . This limited their use as they became so wet at speed as to keep one - third of them useless . The others were mounted in open positions on the superstructure . These guns fired a 50 lb ( 22 . 7 kg ) armor - piercing ( AP ) shell at a muzzle velocity of 3 , 150 ft / s ( 960 m / s ) and a rate of 8 to 9 rounds per minute . The guns could depress to −10 degrees and elevate to 15 degrees . The guns were manually operated , and had a range of train of about 150 degrees . The ships were also initially fitted with two 21 inch ( 533 mm ) torpedo tube s for the Bliss - Leavitt Mark 3 torpedo . Armor suite . Fire control limitations also explain the lack of deck armor that continued onward in this design . The armor suite also displayed other signs of transition with a heavy belt , and mid - grade 6 . 5 " casement armor for the secondary battery and internal partitions to limit damage . The entire horizontal armor scheme was designed to stop shells at very shallow angles of attack ; the anticipated range of engagement meant that incoming fire would be at a relatively flat trajectory , and the danger of high - arcing plunging fire was considered minimal , given the poor performance of contemporary fire - control systems at extreme ranges . The idea being to cause the armor - piercing shells to burst on the thin deck armor and have the splinters of the shell caught on the even thinner 1 " STS steel plate deck below the decapping armor above . This was a rational thought in the light of the known technology of the time . Unfortunately , better fire control systems could and would be installed with relative ease , while refitting armor on existing battleships would be very hard . The idea of plunging fire would not be addressed until the all or nothing scheme of the s two classes after the " Wyoming " class . The main armor belt remained at 11 " tapering to 9 " enough to protect against 12 " naval guns of the period . Engine design . " Wyoming " was the final battleship class in the United States to employ direct drive steam turbines without cruising turbines for power . In subsequent designs , geared cruising turbines ( supplementing direct drive turbines ) , geared steam turbines , triple - expansion steam engines , and turbo - electric drive were all found to give better range for fuel expended . Upgrades . In 1919 , a refit reduced the secondary armament to 16 5 inch / 51 caliber ( 127 mm ) guns and added two 3 inch / 50 caliber ( 76 mm ) anti - aircraft ( AA ) guns . The 5 inch guns were reduced as the mounts near the ends of the ship were difficult to work in any kind of sea . Modernization began in 1925 , finishing in 1927 . This included anti - torpedo blisters giving them broader beams and greater displacement , and also thicker deck armor . Four White - Forster oil - fired boilers replaced the 12 previous Babcock and Wilcox coal - fired boilers with no loss of power , resulting in only a single smoke stack . The masts were reduced to a single cage mast . Both ships were outfitted with newer gunfire controls . Some of the 5 " secondary battery was moved to the superstructure . The 3 " AA battery was increased to eight guns and the torpedo tubes were removed . An aircraft catapult and facilities for three floatplanes ( typically the Curtiss SOC Seagull from 1935 ) were added . " Arkansas " was primarily used for training cruises until World War II , during which she received a second modernization in 1942 . The 5 " secondary battery was reduced to six guns and the 3 " AA battery was increased to 10 guns . The attack on Pearl Harbor had shown the need for significant light AA armament on all ships , so 36 40 mm Bofors guns in quadruple mounts were added , along with 26 20 mm Oerlikon guns in single mounts . Due to the Washington Naval Treaty , " Wyoming " was partially disarmed in 1932 and used as a gunnery training ship for the rest of her career . During World War II , all her 12 " guns were removed and additional 5 " ( 127 mm ) dual purpose guns ( in several different mountings ) and other guns were added , the ship becoming an urgently needed anti - aircraft training platform . History . Despite the class name , " Arkansas " preceded " Wyoming " both in construction and commissioning , although both were commissioned during September 1912 . As the class was fitted with coal - fired boilers , both " Wyoming " and " Arkansas " were able to operate with the British Grand Fleet in the then - oil - deprived North Sea during World War I . Before the war , they served in the Atlantic Fleet and afterwards in both the Atlantic and Pacific , with modernization following in 1925 - 27 . Both ships served in both world wars , and like many older American ships were quickly retired at the end of the second . " Wyoming " marked the end of the class ' nearly 35 years of service when decommissioned 1 August 1947 for scrapping . " Arkansas " had already been sunk during nuclear testing in the Pacific . Notes . Footnotes Citations References . Online sources