An essentially continuous evolution from sailing era ships of the line and early steam era ironclads, battleships are the largest and most powerful naval warships of the late 19th through mid 20th century. The advent of the Royal Navy's revolutionary HMS Dreadnought in 1906 rendered all prior battleships obsolete and triggered an international "battleship race" in which every major naval power (and even many minor powers) sought to gain strategic advantage over geopolitical rivals by constructing the largest possible numbers of the most capable new warships possible.
The signature characteristics of dreadnought battleshihps are an "all big gun" main gun battery of large-caliber naval artillery pieces, a limited secondary gun battery for defense against destroyers and torpedo boats (and later against aircraft attacks), heavy steel armor protection to withstand sustained engagements against similarly armed battleships, and trans-oceanic mobility with steam propulsion.
Dreadnought Battleships
Historically, Congress authorized the Mississippi class predreadnoughts in the 1903 naval budget but did not authorize the South Carolina class dreadnoughts until the 1905 naval budget; no battleships were authorized in 1904. In this alternate history, the Navy avoids wasting 1904 with debate and bureaucratic infighting over the "all big gun" concept, so South Carolina is authorized in 1904 and laid down in 1905. Her fitting-out and sea trials proceed at a less leisurely pace, enabling commissioning in early 1908.
This change effectively pulls the entire early American battleship sequence ahead by two years, beating Germany to become the second nation to commission a dreadnought rather than the third.
South Carolina Class (1904)
The South Carolina class are the U.S. Navy's first "all big gun" battleships, laid down prior to the Royal Navy's eponymous HMS Dreadnought and marking the beginning of the Navy's transition into a global force. Two South Carolinas were authorized.
The South Carolinas' most notable feature is their "all big gun" armament of eight 12"⁄45 Mark 5 naval guns in four two-gun mounts, arranged in superfiring pairs forward and aft. Secondary armament was limited to a large number of 3"⁄50 anti torpedo boat guns fitted in casemates on the sides of the superstructure. As was the norm for battleships in this era, they also carried two 21" tubes for Bliss-Leavitt Mark 3 torpedoes, placed below the waterline on both sides.
The South Carolinas have a four-shaft propulsion plant with paired high and low pressure direct-drive steam turbines on the two inboard shafts and variable triple expansion steam engines on the two outboard shafts. Steam is provided by eighteen coal-fired, superheating water-tube boilers; the turbines have five boilers for each pair and the more economical triple-expansion engines have four boilers each. The system produces a combined total of 22,000 horsepower, enbling a design speed of 21 knots; with the triple expansion engines alone, a range of nearly 7,000 nautical miles can be reached at an economical ten knots.
(This alternate South Carolina differs from her historical counterpart primarily in being authorized at a slightly larger standard displacement of 18,000 rather than 16,000 long tons, which the Navy had historically argued for as the minimum standard set by contemporary foreign battleships. The additional tonnage enables the adoption of the above described four-shaft hybrid propulsion system, as opposed to a more conservative and less powerful two-shaft propulsion with triple-expansion engines for 18.5 knots.)
Delaware Class (1906)
The Delaware class are the U.S. Navy's second class of dreadnought battleships, driven by popular perception that the small South Carolina class is far less powerful than Dreadnought, even though the South Carolina actually had an equal broadside of eight 12" guns and superior armor protection. This causes Congress to authorize this and subsequent battleship classes with no specific tonnage limit, only a cost ceiling.
In order to "match" (actually exceed) Dreadnought's firepower, the Delawares add a fifth two-gun turret amidships, placed behind the funnels but forward of the aft mast. The aft superstructure therefore seperated the #3 turret from the stern pair, which had the #4 turret superfiring over the #5 turret. In addition, the secondary guns were changed to 5"⁄50 Mark 6 guns to provide more effective defense against torpedo boats. Due to their size and weight, most of the 5" guns were placed in casemates below the main deck rather than in the superstructure, four amidships on each side. Two additional open mounts were placed on the forward deck, and two on the aft deck. Two 21" tubes for Bliss-Leavitt Mark 2 torpedoes were again fitted.
The Delawares repeat the hybrid propulsion arrangement introduced on the South Carolinas, with a modest increase in total output to 25,000 horsepower to maintain the same 21-knot speed as their older sisters despite their slightly heavier displacement of 20,000 tons. The Navy's range requirement for this class is slightly reduced to 6,000 nautical miles at ten knots, which reduces the amount of fuel bunkerage required.
(The alternate Delawares are the same size as their historical counterparts. They differ in having the same hybrid propulsion plant as the alternate South Carolinas, and in placing the #3 turret amidships, whereas the counterpart placed #3, #4, and #5 turrets all aft with #3 superfiring, #4 and #5 as a back-to-back pair at deck level. This layout better supported the heavier superfiring turret by placing it further forward in the ship, but meant it could not safely fire directly over the forward-pointing #4; while all ten guns could fire on either broadside, only #5 could fire aft.)
Florida Class (1907)
The Florida class battleships were slightly improved and enlarged repeats of the Delaware class.
The main gun armament of the Floridas is identical to that of the preceding Delawares, while the secondary armament was further improved to the new 5"⁄51 Mark Mark 7. This was an excellent medium caliber gun with high muzzle velocity and good accuracy, and remained the USN's standard battleship and armored cruiser secondary gun throughout the next two and a half decades. Due to the further increased weight of these guns, all were casemate mounted below the main deck, eight on each side. The usual two 21" submerged torpedo tubes completed the armament as built.
In 1917, both of these battleships were refitted with four 3"⁄23 anti-aircraft guns, two on the forward deck and two on the aft superstructure.
(The alternate Floridas are closer to their historical counterparts since a four-shaft layout was now adopted historically; the divergences on this class are pretty much just what they carry forward from the previous alternate battleships, hybrid propulsion and a 2-1-2 layout. They do not recieve a second refit in 1925, as they are retired under the terms of the alternate Washington Naval Treaty.)
Wyoming Class (1908)
The Wyoming class battleships were the first U.S. Navy dreadnoughts to be designed with operational knowledge from prior dreadnoughts, as well as from the ongoing cruise of the Great White Fleet's predreadnoughts. This resulted in a number of substantial changes in design, primarily oriented towards increasing seaworthiness and reducing how "wet" the ship was, most visibly a full-length forecastle which effecively raised the amidships casemates by a half deck level.
Although newfound operational experience now demonstrated the practical limitations of amidships turrets and the Navy had in fact already considered triple mountings as early as the South Carolinas, there was not enough time to embrace such a major change in layout. The Wyomings therefore mounted their twelve guns in six two-gun turrets, with a superfiring pair forward, a back-to-back deck level pair amidships, and a superfiring pair aft. The 12"⁄50 Mark 7 was a new and slightly more powerful main gun with a longer barrel and enlarged breech chamber, allowing it to fire the same shells at a higher velocity. The longer hull enabled one more 5" casemates on each side for a total of twenty secondary guns, along with the obligatory two 21" submerged torpedo tubes.
As with the Florida class, both of these battleships recieved a 1917 refit adding four 3"⁄23 anti-aircraft guns, two on the forward deck and two on the aft superstructure.
New York Class (1909)
The New York class battleships were the last "regular" dreadnoughts in U.S. Navy service.
The New Yorks made the desired switch to triple turrets, enabling the same twelve-gun main battery as the Wyomings to now be carried in fore and aft superfiring pairs. Secondary armament remained the same as Wyoming, but the torpedo armament was increased to four submerged tubes to take advantage of the potential presented by the new, longer-range Bliss-Leavitt Mark 3 torpedo.
Due to their larger size and "cleaner" layout, the New Yorks are able to accomodate substantially more 3"⁄23 anti-aircraft guns in their 1917 refit than other U.S. Navy dreadnoughts, with two on the forward deck abeam the #2 turret, four in the forward superstructure, two in the aft superstructure, and two on the stern deck abeam the #4 turret.
After returning home from overseas service at the end of 1918, both New Yorks recieved an additional refit, with the 5" guns being removed from the furthest forward and aft hull casemates in order to improve seaworthiness. A much more comprehensive modernization followed in 1925, with all of the hull casemates and torpedo tubes being completely removed and plated over, the superstructure substantially reconstructed with new tripod masts and above-deck casemates for six 5" guns, and the original coal-fired boilers replaced with a set of six oil-fired ones.
(The New Yorks are the most visibly changed of the alternate early dreadnoughts, since the adoption of four triple main battery turrets eliminates the amidships turrets entirely. This is not as radical a decision as it may seem, since the Bureau of Ordnance did not successfully test the new 14" gun until 1910; with the battleship construction timeline moved up but other historical events remaining semi-fixed, the adoption of the new guns falls back by one class.)
Standard Battleships
The "Standard Type" battleships of 1910-1920 are a set of five successive superdreadnought battleship classes (and a sixth unbuilt class) which follow a set of standardized operational characteristics in order to allow all five classes to seamlessly operate together. The specified characteristics are an all-centerline main gun arrangement with no amidships turrets, a range of 8,000 nautical miles at cruise speed, a top speed of 21 knots, and a tactical turn radius of 700 yards.
For the most part, this is a formalization of the advantageous characteristics that most U.S. Navy battleships already have. The relative similarity in performance between its dreadnought battleship classes has enabled an excellent level of interoperability between classes. It is also a political compromise between the Navy's desire to continue the "two battleships per year" naval expansion established by President Roosevelt with Congress' desire to limit growth in size and cost.
Nevada Class (1910)
The Nevada class are the first Standard type battleships and the first U.S. Navy "superdreadnoughts", representing the first major leap in American battleship design since the South Carolina class.
The Nevadas are armed with twelve 14"⁄45 Mark 1 naval guns in four three-gun turrets, arranged in superfiring forward and aft pairs. The new guns offer a substantial increase in range, armor penetration, and destructive capability over 12" guns, maintaining general parity with the Royal Navy's 13.5"⁄45 Mark V and (in principle) the High Seas Fleet's 35 cm ⁄45. In an effort to address the seaworthiness concerns raised with the placement of previous American battleships' secondary guns, the eighteen secondary 5"⁄51 guns are divided between six casemates on the sides of the foredeck, four casemates on the sides of the forward superstructure, and four two-gun deck turrets placed amidships (abeam of the funnel and aft mast). This is the first use of secondary gun turrets on a new battleship since the predreadnoughts, but for relatively small-caliber defensive guns rather than an intermediate caliber offensive battery.
In addition to their new armament, the Nevadas introduce two important technical improvements in propulsion: their boilers are oil-fired rather than coal-fired, and the introduction of geared cruising turbines enables symmetric all-turbine propulsion for the first time in the U.S. battleships of this timeline. All four shafts are directly driven by a high pressure main turbine; the cruising turbines are four additional low pressure geared turbines which are connected to the shafts via clutches. Reverse operation is enabled by astern power sections integrated into the high pressure turbines. Total output was 30,000 horsepower, enabling the desired speed of 21 knots.
(The alternate Nevada class avoids sending Congress a rough estimate draft rather than a finalized design for approval, so she is properly sized for the intended twelve-gun configuration. She also continues the four-shaft layout from prior alternate USN battleships, whereas their USN counterparts had made a premature attempt at four-shaft all-turbine propulsion with the Wyomings and then switched back to two-shaft triple expansion on the Floridas and New Yorks. The historical Nevadas somewhat hesitantly used two-shaft turbine on one Nevada and two-shaft triple expansion on the other.)
Pennsylvania Class (1911)
The Pennsylvania class are in most respects a repeat of the Nevada class, incorporating numerous evolutionary improvements but no truly major changes. These were the newest and most advanced U.S. Navy battleships in service when the nation entered World War I.
The most significant improvement adopted on the Pennsylvanias is an improved hull; they are built at the same 30,000 ton displacement as the previous class but their physical dimensions are increased. This improves their hydrodynamic streamlining and allows the desired speed to be achieved with slightly lighter propulsion machinery, freeing up tonnage for slightly increased armor protection.
New Mexico Class (1912)
The New Mexico class are the third Standard type battleships. Once again, they were in most respects repeat vessels, although this time with a greater scope of improvements permitted by an increase in total tonnage to 32,000 long tons.
The New Mexicos are armed with twelve 14"⁄50 Mark 4 naval guns in four three-gun turrets, arranged in superfiring forward and aft pairs. These are a slightly longer and higher-velocity upgrade of the prior 14"⁄45 guns, yielding superior accuracy, range, and armor penetration. The layout of the secondary armament is a further development of the new layout utilized for the Nevada and New Mexico classes: all twenty secondary 5"e;⁄51 guns are mounted above the main deck, divided between six two-gun wing turrets (two forward, two amidships, and two aft) and eight upper deck casemates in the sides of the forward and aft superstructures.
Like their historical counterparts, the New Mexicos are the first warships in the world to utilize turboelectric propulsion. Two high-pressure and two low-pressure steam turbines turn high output electrical generators, which in turn power electric drive motors on the propeller shafts. This completely eliminates the operating speed issues associated with direct drive turbines, enabling both the turbines and the propellers to operate at optimized rotation speeds instead of being forced to run at the same speed. In addition, it substantially enhances the maneuverability of the ships by enabling nearly instant and fully independent throttling and reversing of any shaft, including full power operation in reverse. Steam was provided by a reduced set of nine oil-fired boilers.
Tennessee Class (1913)
The Tenneseee class are the fourth Standard type battleships. Since the Secretary of the Navy refused to authorize a further increase in tonnage or the adoption of 16" main guns, they are "simply" refined repeats of the New Mexico class.
Because of the repeat nature of the Tenneseees, the notorious Senator Benjamin Tillman stirs up substantial controversy over the Congressional authorization for these "weak" new battleships. He demands that the Navy jump straight to a "maximum battleship" of the largest possible size and firepower, and that in the meantime Congress should authorize no new battleships at all. Fortunately, he does not achieve sufficient political traction to cancel or limit the production of the Tennesees.
(The Tillman controversy is a relatively fixed point in history since it is tied to the Senator's rise to Chairman of the Senate Naval Appropriations Committee in 1913. Thus, in this timeline he attacks the Tennesee class rather than then Pennsylvania class). With the "slide" in the timeline, the more immediate complaint of continual increases in size and cost without a corresponding improvement in firepower is addressed by pointing out that the next class is already meant to fit more powerful 16" guns on essentially the same hull, and that said upgrade can be backfitted to this year's Tennesees.
Colorado Class (1914 ⁄ 1915)
The Colorado class are the final Standard type battleships to actually be built. Congress authorized two battleships of this class in 1914 and two more in 1915, with the Navy securing the funding for an "extra" (USS Utah) with the money from selling the two Missisippi class predreadnoughts to Greece.
The Colorados are armed with eight 16"⁄ Mark 2 naval guns in four two-gun turrets. Congress and the Secretary of the Navy had been extremely reluctant to accept further increases in battleship size and cost, but by 1914 the Royal Navy's 15" armed Queen Elizabeth class battleships were already entering service and this gave the United States little choice but to "keep up". Nonetheless, the modest proposal of a repeat Tennesee with two-gun 16" mounts replacing the three-gun 14" mounts was selected over the more ambitious one of a significantly larger battleship which would maintain the four three-gun mount pattern.
South Dakota Class (1916)
The South Dakota class adhered to the Standard type characteristics, but were much larger than previous Standards. Congress authorized four of these battleships in 1916 with three more for 1917 and three more for 1918, but battleship construction was suspended in 1917 to prioritize immediately necessary escort vessels. Construction then resumed in 1920, but was cancelled for the Washington Naval Treaty of 1922; the four which had been laid down were scrapped in place.
The South Dakotas would have been armed with twelve 16"⁄50 Mark 2 naval guns in four three-gun turrets, thus returning to the "usual" layout of the Standards but with 16" guns. The secondary armament would have increased in caliber to 6"⁄53 guns, something that had been long desired for increased effective range against destroyers and torpedo boats but had not been possible without a substantial increase in size.
Overall, the South Dakotas would have been the most powerful battleships of the early 1920s, exceeding the Royal Navy's Queen Elizabeth class battleships and Admiral class battlecruisers. However, they would have soon been exceeded by the absolutely stupendous N3 and G3 classes, demonstrating the continued "battleship race" which the Washington Naval Treaty prevented.