Very briefly about the alternative.
It is based on two messages. First, that since second half of XIX century the development of a worldwide weapons system has ceased to keep up with technical progress, became scholastic, and its path became similar to Brownian movement. The proposed alternative is an attempt to optimize the overall weapons system. One of the conclusions of this optimization is the recognition of artillery as the main type of weapons.
Second, the alternate United States is used as an illustration of this optimization, because exactly the evolution of the American weapons system contained many elements that were closest to the proposed optimum. If we make only one assumption that in the development of their armed forces the Americans were more likely to rely not on classical European knowledge, but on their own practical experience, then we can assume that the American weapons system would have taken a more optimal path.
The timeline of this alternative differs little from the real history up to 1939. Unless, the United States is more isolationist and more committed to the Monroe Doctrine. However, this has little effect at first. Maybe only, Cuba is annexed instead of Philippines, and the Philippines is granted independence under United States patronage, with a US base in the Manila Gulf. But by 1939 the isolationist policy giving a result, oddly enough, somewhat opposite to indifferent neutrality.
However, the isolation gives significant deviations in part of the weapon development, combat engagement, and military organization. The starting point for alternative changes was an experience of the Civil War. For the Navy, this was the moment the New Navy creating. Herewith, the greater importance was of all the previous experience in the development of the US naval forces from the very moment the obtaining of independence. So let's start with a real-historical preamble to understand what the New Fleet could be if the Americans were based on their own experience.
Some images based on the work of Craig Hoefer, for which many thanks to him. I refer to some of his drawings in their entirety to show the full line of development.
In the initial, most difficult period for the young American state, 1775-1815 - the War of Independence, the Quasi-War with France and the War of 1812 - the US Navy had no ships of the line and did not know linear or any other squadron tactics. There were three reasons for this. The first was financial: the scarcity of the federal budget, which made building and maintenance of such large ships extremely difficult. Another reason is operational-tactical: the ships-of-line's characteristics assumed low speed and, to a certain extent, a limited range, which did not meet the needs of the united American states, given their fleet quantitative backlog and huge coastline. Finally, the third reason was strictly conceptual: it is impossible to resist a numerically superior enemy with his own tactics. Moreover, even at then age, the shipbuilder of the American navy, Joshua Humphreys, aimed not only at parity with the former metropolis, but also at superiority. As an experienced shipbuilder, he knew how inert his professional environment was. The shipbuilder bears a huge responsibility for the fate of an expensive ship, for the lives of the crew, and, ultimately, for the sea power of the country. Therefore, the builders of warships shied away from experimentation, using reliable time-tested solutions. The ships of the late 18th century differed little from those of the 17th century. In order to bypass rivals when numerical parity was impossible, the Americans needed to get out from the plane of established views into a new quality. At the same time, the inert mass of the former fleets could only follow the revolutionary outlook, and the Americans would have a chance to come out ahead in matters of fleet building.
Humphreys have proposed a large frigates that carried ships-of-line's long-range 24-pound guns on the main gun deck instead of the usual for frigates 18-pounders (in a smaller number, of course), but surpassed ships-of-line in mobility. They carried 32-pound carronades on the forecastle and quarterdeck. Ranked as 44-gun (but actually carrying a lot more barrels), the large frigates would certainly outperform any normal, as maximum 38-gun frigate, and under certain conditions had a chance against a ships-of-line. Similar frigates have existed before too, but in the hands of American sailors, thanks for their high qualifications, and the Humphreys design's superior characteristics, the large frigates demonstrated its worth during the War of 1812. Of no small importance was the very strong and durable material of the hulls of large Humphreys' frigates, a special type of American oak - live oak. Although the Americans had too few large frigates to do everything that entrusted to them, nevertheless, Humphreys' calculation was justified - to neutralize only three large frigates, the British had to attract significant forces.
The effect produced by large frigates gave rise to consequences that were important for the US Navy: this type was highly appreciated there, and it further developed, including with the transition to a sail-steam drive. If the "oak frigates" created under the Humphreys' sole influence, the steam ships were building by different shipbuilders, while the consolidator and guarantor of the sequence of development during this period became the Chief of the Bureau of Steam Engineering, Benjamin Franklin Isherwood. He was the designer of most of the ship propulsion systems of then time, gradually improving them from model to model and developing a reliable and effective design. His views led to the transformation of the steam engine from an auxiliary propulsion unit into the main one, and then into the only one.
And the last pre-war sailing-steam 1st class frigate of the US Navy - laid down in 1855, USS Niagara - marked a new turn in the large frigates' development. Designed by George Steers, the creator of the very yacht America, after which the main sailing trophy named, Niagara was the first warship with clipper lines and the first warship with the wider hull behind the mid-frame. In fact, become a corvette (in the American classification of that time - a sloop-of-war), that is, a ship with a single continuous open gun deck from bow to stern, the frigate in the person of Niagara, naturally, lost exactly the battery of close battle carronades, remaining only with a battery of long-range cannons. An equally important factor was that, unlike classmates, this Niagara's battery was a homogeneous of 12 new 11-inch Dahlgren guns, capable of firing both solid balls and bombs. In addition, at Niagara, not only stern and bow guns were installed on the rotary mounts, but also onboard ones, although the latter - with small sectors of fire.
One of the problems of the emerged ship's screw movers was the need to pass the propeller shaft through the sternpost, which weakened or complicated. In addition, the location of the propeller made difficult the rudder installation. These problems tried to solve by passing the shaft to side of the sternpost. In order to reduce the thrust misalignment tried to pass the shaft as close to the stem as possible. However, this led to the fact that the propeller and the rudder interfered with each other. Therefore, the screw was carrying out behind the rudder blade. However, too long a free shaft end meant excessive vibration.
In 1860, the Navy replenished with one more iconic ship. Built by the renowned clipper builder John Willis Griffiths, the 67-meter 1500-ton sloop (II class frigate) Pawnee was first in the US Navy which received two screws installed symmetrically relative to diametral plane without complicating the sternpost and rudder joint, with a large deflection, and, therefore, with short shafts. They rotated by a single engine through a gear transmission in opposite directions.
Other notable feature of the Pawnee was the reduced rig and the absence of a bowsprit - the sail on it became auxiliary propulsion.
Initially its battery consisted of four 11-inch Dahlgrens on slewing rails, similar to those of Niagara, with 12-foot ports. Its structural strength was such that in 1863 it was addition armed with one 50- and one 100-pound rifled cannons.
The new quality of the artillery component forced a change the signs of the US Navy ships' classification. Previously, neither due to the absence of a closed gun deck nor to the rig, the Pawnee would cannot have been considered a frigate. However, now it was similar to the latest generation large frigates not only by these features. The ability to put his artillery on the large frigates line distinguished namely him from an ordinary sloop.
It was that exactly with 11-inch Dahlgren was soon armed the American ship of type unseen before. Born in the Civil War and differed of many features from everything that existed before, this new type could get name by any of these features. Moreover, not only could. In Europe, which copied the form, but was not familiar with background of the birth of this class, it called a monitor, an ironclad, or a battleship. However, this class was born under a name that accurately reveals its essence, its artillery nature - a battery. Thus refuting the opinion once again that the first capital ship carrying only main battery guns was Dreadnought. After all, a battery is an artillery organizational unit performing a single mission, and therefore homogeneous.
Another point is also no less important. If in the sailing fleet were mattered whether you approached the enemy from the leeward side or from the windward, now only artillery decided everything. The warship became artillery not only by the gun was its main weapon; now its tactics, and its operativeness, and its strategy became exclusively artillery too.
The Secretary's Annual Report for 1861 stated that "No sailing vessels have been ordered to be built, for steam as well as heavy ordnance, has become an indispensable element of the most efficient naval power."
The 1865 Secretary's Annual Report stated: " ...The skillful disposition of the sails ... is no longer necessary ... To confine himself to seamanship, without the ability to manage the steam engine, will result in his [the naval officer's] taking a secondary position..."
The title of the founder of a new type received not by casemate battery but by Monitor because in comparison just with casemate the Monitor represented a new word only in artillery alone. Although Virginia carried 12, well, let without howitzers - 10 barrels, and Monitor only 2, the casemate battery could shoot in direction of the target only a smaller part of them. In addition, to lock the target into a narrow sector of fire of the casemate installation, it was necessary to orient the ship to a certain position. The Monitor, on the other hand, with its rotating turret and slopping funnels, has an almost circular sector of both its barrels. It did not carry a dead mass of unnecessary guns, it used them effectively, and the saved weight could used to increase the power of artillery or the thickness of armor. With two artillery schemes in front of them, progress took the best.
So, Britain cherished the colonies and therefore began to armor the cruisers. Unionist America needed a means for operations near the coast of the rebellious states, so there not very naval designers built not very sea ships - without boards, without masts, without sails - and gave them under the command of not very sea captains-artillerymen. In their warships the Americans saw not armed vessel, but, on the contrary, floating guns.
However, when the tasks of the internal war received this satisfactory remedy, the admirals of the Navy decided to attend to the threat of foreign intervention. During the Civil War, speed tactics were confirmed by the experience of South raiders in the eyes of the Americans. Therefore, when Britain began to build armored frigates, the Americans resorted to a proven means and responded with large frigates again. Niagara's characteristics were in line with the Navy's focus on ocean-going warships, and it proved to be an obvious candidate for replication. Thus, his influence on the development of the design of the large frigate was more important to the Navy than his own career.
In March 1962, the rebuilding of the large frigate Roanoke into a screw seagoing battery began. It was proposed cut to a corvette, to deprive the mast, to strengthen the structure for accommodate the side armor and 4 armored turrets, similar to those of the Passaic battery class. However, it soon became clear that the load would be too great for the ship's hull.
At the same time, the question was being decided, whether to support conceptually the construction of both types of ships, batteries and large frigates, or either one of them, or choose something mean between of them. The first option threatened by the fact that with limited funding both batteries and large frigates were too few for each to satisfactorily fulfill its task. The variant with armored frigates, combining the properties of these types, was already adopted by the British, and, as before, to resist the large British fleet with its tactics was impossible. If you build the Navy from any one type, then it is obvious that battery is completely incapable of ocean operations, while a large frigate with coastal ones, at the very least, would cope. This had to rely on speed again. It was clear that the armor would not allow the British ship to be as fast as possible, in which case the armored ship would not be able to destroy the high-speed frigate. However, conversely, a large frigate could not destroy an armored one too, if its protection consists only of a distance beyond the control of the enemy artillery. To get out of this situation, the Americans needed to artillery that would outrange the enemy one. To do this, they were going to use 8-inch rifled Parrott (7300 m/35°, 7.5 t, 86-91 kg) or Dahlgren on large frigates.
So, the admirals needed a ship for naval operations, for which the Roanoke conversion project originally established was not capable. Therefore, from reducing the load due to the abandonment of some of the turrets, they came to a more radical one: to the abandonment of all armor - both onboard and turret. So far there were not enough rifles, only one of mount get their. All the same standard smoothbore 11-inch Dahlgren's of similar weigh (3300 m/15°, 7.1 t, 75 kg) was putted temporarily on the rest mounts. However, the planned installation of an additional cylinder of the main engine, as well as an auxiliary cylinder and machines for turning the turrets (albeit weaker than the design ones), was completed. The dismantling of the masts that had already been made was considered a mistake, but there was no way back. If single-gun rotary mounts had a design that allowed them to be brought into the ports of both port and starboard, where the rigging did not interfere with a significant sector of fire, then the steam-driven mount was fixed in the diametral plane, and multiple rigging seriously limited their sector of fire. However, now a third fewer guns than Niagara, gave of one barrel larger side salvo. With the Roanoke conversion, Isherwood's goal of only the mechanical propulsion for a large frigate was achieved. After the war, all the frigates remaining in the ranks underwent a similar modernization.