To the student of current U.S.-China relations, the geopolitical dynamics of the 1840s would seem strikingly familiar. The United States, a rising industrial power, sought to rapidly expand its navy because of a belief that its domestic political system was under threat from encirclement by the United Kingdom, the leading maritime power. The United Kingdom, in turn, sought to check U.S. territorial expansion, opposing U.S. annexation of Texas, a nominally independent republic. Tensions between the two powers persisted and occasionally threatened to break out into war.
Amid this volatility, events were unfolding that would dramatically transform naval warfare. On an afternoon in August 1837, a U.S. naval officer entered the Trafalgar Tavern, a pub on the south bank of the River Thames. Extraordinarily wealthy and extremely ambitious, Captain Robert F. Stockton was the scion of New Jersey’s most powerful political dynasty. Once again on an extended period of leave from a seemingly stalled naval career, Stockton was in London tending to personal business. He had agreed to witness a demonstration of an invention by John Ericsson, a 34-year-old engineer who had migrated to London from his native Sweden a decade earlier.1
Ericsson possessed an unparalleled genius for all things mechanical, but his time in London had produced only career setbacks, including missing out on an opportunity to manufacture the world’s first passenger locomotive. By the time he met Stockton, Ericsson was dispirited and broke, and he was desperately trying to interest investors in his latest innovation, a new method for steamship propulsion.2
Since their invention by Robert Fulton in 1807, steamships had used paddle wheels to flail their way across the waters. These highly inefficient devices raised a ship’s center of gravity and dangerously increased the degree of roll during storms. The machinery of paddle engines took up valuable deck space that otherwise might be used for cargo or guns, while their large, round wheels above the waterline presented a perfect target for disabling fire during combat.3
What Ericsson proposed was a principle known since the time of Archimedes, a spiraling helix below the waterline that would push water past the ship—in other words, what would become known as the maritime propeller. Ericsson had demonstrated a prototype of his invention to the Royal Navy, which rejected the idea on the mistaken belief that a ship could not be effectively propelled from the stern.4
But where the Royal Navy saw folly, Stockton saw a chance to revive his faltering naval career by rebranding himself as a technological reformer. The meeting at Trafalgar Tavern ended with Stockton commissioning Ericsson to produce plans for a naval vessel.5 The warship Ericsson proposed included several innovations. Most notably, it used wrought iron for its main guns, rather than the traditional cast iron.6 Thanks to his political connections to the Tyler administration, Stockton secured authorization to build a 600-ton vessel. He was given a relatively free hand to construct and fit out his experimental ship with Ericsson’s help.7 On 7 September 1843, the USS Princeton was launched, becoming the U.S. Navy’s first propeller-driven warship.8
To demonstrate his technological marvel to the highest levels of the government, Stockton hosted a series of pleasure cruises down the Potomac River, the last and grandest of which was held on 28 February 1844. With the crew manning the rails, Captain Stockton welcomed aboard distinguished guests including President John Tyler and most of the Cabinet secretaries, several members of Congress, high-ranking officials from the Army and Navy, and prominent members of Washington society.
What should have been a triumph for Stockton turned into a disaster. During the final demonstration of the ship’s main wrought-iron gun, the Peacemaker, the cannon exploded, killing and injuring several passengers. For President Tyler, who narrowly escaped injury himself, the Peacemaker explosion was a political catastrophe. Among the dead were Secretary of State Abel Upshur and Secretary of the Navy Thomas Gilmer, key members of Tyler’s politically isolated administration.9 The explosion likely ended Tyler’s political career, setting in motion a series of events that would lead to his withdrawal from the 1844 presidential election.10
Another casualty of the Peacemaker incident was the relationship between Stockton and Ericsson. Already seething over being left behind in New York while Stockton took credit for the Princeton, Ericsson refused Stockton’s request to testify to the Court of Inquiry convened to review the accident.11 Stockton, in turn, denied payment to Ericsson for his work on the ship.12 In addition, while Ericsson may have warned Stockton about the Peacemaker, false rumors spread in naval circles that the explosion had been Ericsson’s fault.13
The Princeton disaster may thus have slowed adoption of the propeller by removing some of its chief advocates. Ironically, two of the greatest champions of U.S. naval development had been Upshur and Gilmer, both killed in the Peacemaker blast.14 With the outbreak of the Mexican-American War, Stockton turned his attention from technological reform to seek military glory in California. Ericsson, meanwhile, would build several more propeller-driven ships over the next 17 years; but whether because of mutual suspicion or for another reason, he built none for the U.S. Navy.15
In the years leading up to the Civil War, the Navy would launch only six screw frigates, along with a comparable number of sloops and smaller vessels. Mostly built at Navy shipyards rather than by civilian contractors, the screw steamers suffered from engine problems and maintenance issues.16 By 1860, on the eve of the secession crisis, the U.S. screw fleet was in disarray, with four of six frigates under repair, or “in ordinary.”17
The British Experience
At the same time Ericsson was developing his prototype, a farmer and amateur inventor named Francis Pettit Smith was working on his own propeller design, resulting in a small demonstration boat eponymously christened the Francis Smith. A few weeks after rejecting Ericsson’s designs in 1837, the Royal Navy received reports from coast watchers of the Francis Smith making headway in a storm, seemingly disproving concerns about the steerability of a stern-propelled ship.18
In 1839 Smith built a second ship, the schooner Archimedes, which was used in a series of trials supervised by the Admiralty. Satisfied by the trials and encouraged by the brilliant engineer Isambard Kingdom Brunel, the Royal Navy ordered the addition of a screw propeller to the sloop HMS Rattler, which was already under construction.
Launched on 13 April 1843, the Rattler would vie with the Princeton for the distinction of being the world’s first screw-propeller warship.19 To test the capabilities of screw propulsion, the Admiralty engaged the Rattler in a series of trials against the comparably sized paddle sloop HMS Alecto, the most dramatic of which occurred on 3 April 1845, featuring a “tug-o-war” between the two ships. With a line connected between their sterns, the Rattler and Alecto steamed in opposite directions. At first the Alecto had the advantage, but the Rattler slowly gained momentum and began to tug the Alecto, its paddle wheels splashing uselessly.20
The contest between the Rattler and Alecto went down in popular lore as the definitive demonstration of the superiority of the propeller. In reality, the results of the Rattler trials were far more mixed, showing little to no efficiency advantages, likely because of the era’s lack of understanding of the hydrodynamics of screw propulsion. Propeller design evolved through a process of trial and error.21 Complicating early designs were propeller shafts’ higher rates of revolution, which produced vibrations that wreaked havoc on the structures of wooden warships.22 Effective use of these propellers would require the adoption of another innovation, the iron-hulled vessel.
The dramatic Rattler trials were not the only experiments the Royal Navy conducted into the new technology. Fearful of war with France, and later fighting the Russians in Crimea, the Admiralty engaged in a rapid and multifaceted expansion of its screw steamer fleet, buying existing ships, retrofitting old hulls, and constructing new vessels.23 The result was that the Royal Navy far outpaced the U.S. Navy in adopting the propeller in the years preceding the Civil War, both in absolute numbers, and as a percentage of its total fleet. By 1856, the Royal Navy would possess 348 screw-propelled vessels, out of a total of 735 (47 percent), compared to just nine screw ships of the 76 vessels comprising the U.S. Navy (12 percent).24 Five years later, the Royal Navy had increased the number (and proportion) of these vessels to 468 of 735 (63 percent), while the United States had increased to 31 of 90 (30 percent).25
Disruptive Technology
The propeller is an example of what management theorist Clayton Christensen termed a “disruptive technology.” Functionally immature at their introduction, disruptive technologies initially find few consumers. Established firms ignore them. Eventually, however, disruptive technologies overtake and supplant mainstream products and often drive leading firms out of business.26 For example, many early business computer firms such as Digital Equipment Corporation initially dismissed the personal computer market, only to be driven out of business by the success of companies such as Apple.27
The propeller would disrupt paddle wheels as the dominant form of maritime propulsion, and in the United States, the process followed the typical pattern of slow initial adoption followed by gradual universal usage. But in the United Kingdom, the Royal Navy quickly embraced propeller technology. What explains the difference?
Certainly, part of the answer is that the British identified the technology’s adoption as serving their national interest, while in the United States, the imperative to adopt was less keenly felt, perhaps as an indirect result of the Princeton disaster. However, even where the will exists to adopt a disruptive technology, organizations may fail to do so for reasons explained by resource dependence theory (RDT).28 RDT states that if organization A depends on organization B for necessary resources, then organization B will exert power and influence over organization A.29 Put into context, RDT implies that even if personalities and policies aligned to adopt the propeller, neither the United States nor the United Kingdom could do so without the resources of its broader maritime economy. Adoption required naval architects experienced in designing screw propeller engines; shipyards capable of building them into ships; and seagoing enginemen who would operate and maintain the vessels.
The maritime economies of the United States and United Kingdom in the mid-19th century were very different. Both depended on international trade, but the U.S. merchant fleet focused on the internal market, moving goods along the country’s 6,500 miles of inland waterways.30 This emphasis allowed the United States to tap its seemingly endless supply of natural resources, including producing 5 billion board feet of lumber in 1850.31 By contrast, the United Kingdom of the mid-19th century possessed just 4,000 miles of inland waterways.32 An island nation, the United Kingdom depended on importing raw goods—lumber from the United States and Canada was especially important. But what the United Kingdom lacked in raw goods, it made up for in industrial might, producing four times as much pig iron as the United States at nearly half the cost.33
These attributes shaped the characters of the countries’ merchant fleets. In 1859, the insurance firm Lloyds, which had been producing an inventory of the British merchant fleet for nearly a century, published a register of U.S. ships for the first time. Of the 576 listed steamships built in the United Kingdom, more than 77 percent (444) possessed propellers, while just 39 percent of 239 U.S.-built steamers employed the technology.34 Of the British ships for which Lloyds listed a destination, 73 percent were bound for foreign ports, while in the United States only 25 percent were rated as “seagoing” and thus presumably capable of engaging in international trade.35 In addition, the relative abundance of iron and scarcity of wood in the United Kingdom incentivized British shipbuilders to more quickly convert to iron hulls: The register found that 86 percent of British-built steamships were made of iron, compared to just 12.5 percent of U.S.-built steamships.36
Thus, the U.S. maritime economy, by focusing on internal trade routes and adhering to wood as a cheaper construction material, constrained propeller adoption by neglecting the resources it required. In contrast, the British maritime economy may have created a virtuous cycle of adoption: The use of propellers and iron hulls by a merchant fleet focused on international trade not only provided the resources necessary for the Royal Navy to adopt the propeller, but also created a demand for a propeller-driven Navy that could keep up with and protect its merchant fleet.
Lessons for Great Power Conflict
If the maritime propeller transformed merchant shipping and naval warfare in the 19th century, artificial intelligence (AI) promises to radically transform almost every facet of life in the 21st century. Quoting Thomas Edison, the National Security Commission on Artificial Intelligence noted that AI “holds the secrets which will reorganize the life of the world.” AI already has transformed sectors such as manufacturing and healthcare, and it promises to revolutionize warfare as well, helping militaries “prepare, sense and understand, decide, and execute faster and more efficiently.” A nation possessing an edge in AI technologies may wield a decisive advantage against potential adversaries. China understands this and has invested heavily to ensure that it, and not the United States, leads the world in AI.
As the United States competes for AI dominance, the history of the screw propeller offers at least two lessons. First, success or failure will be determined as much by resource dependence on domestic markets than on any policy decision or budgetary appropriation. Just as the United Kingdom’s maritime economy gave it an advantage in adopting the propeller, China’s domestic market may give it an advantage in developing AI for military use. With more than 1.4 billion consumers and an authoritarian government less constrained by principles of privacy, Chinese AI developers have access to an unrivaled data pool on which to train AI algorithms. Supported by their government, Chinese firms lead the world in facial recognition, so-called smart city networks, and other surveillance technologies. Developed for consumption by (and monitoring of) the Chinese domestic market, these tools may offer the People’s Liberation Army advantages in reconnaissance, targeting, and indications and warning.
However, while resource dependence created an absolute advantage for the United Kingdom over the United States in the mid-19th century, any Chinese advantage in AI today is only relative. The United States still outpaces China in venture capital, education, research and development, and semiconductor production.
Other advantages may prove to be quite enduring. For example, at the time of this writing, U.S. firms lead the world in the development of generative AI—a technology with applications such as ChatGPT that uses algorithms to create communicative content. Generative AI has the potential to transform almost every facet of communication, including areas with direct military application, such as intelligence research and analysis. But this technology will only succeed to the extent that it produces accurate and reliable output. In this regard, the United States’ constitutional protections of free speech may be conducive to generative AI development by neither limiting the data pool through censorship, nor polluting it through propaganda.
This suggests that if trade-offs must be made in U.S. defense research efforts, funding should go to areas where the U.S. already holds comparative advantages and to efforts that are consistent with U.S. values and market demands. Emphasizing the above, rather than trying to beat China at its own game, could help win over U.S. technology firms that may have grown skeptical of cooperating with the Pentagon in recent decades. It also will put the ideological differences between the United States and China in sharp relief for multinational firms torn between the two nations’ competing demands.
Further, carefully planned and centrally directed efforts to adapt disruptive technologies are less effective than scattershot, “see what sticks” approaches. Certainly, the U.S. Navy in the mid-19th century was at a disadvantage compared to the Royal Navy in terms of maritime economic resources. But the United States did itself no favors by holding tight control over its development of the propeller, inhibiting innovation and expansion by building most ships from scratch at government yards. In contrast, the British used a looser, diversified approach. The Admiralty was able to test different propeller and engine designs, explore tactics across ship classes, and develop new ship models in a fairly cost-effective manner.37 In a similar way, the modern U.S. Navy must not try to integrate AI applications only through the standard acquisition and shipbuilding processes. Instead, the Navy should accelerate adaptation and innovation by making greater use of off-the-shelf technologies, as well as retrofitting legacy and mothballed platforms with AI applications to serve as testbeds and operational force multipliers.38
Fortunately, the U.S. Navy avoided war with the technologically superior Royal Navy in the decades following the introduction of the screw propeller. The gap between the two navies was largely closed by the Civil War, with the proliferation of screw-propelled ironclads vital to the Union Navy’s efforts in Southern coastal and littoral waters.39 Ironically, much of the credit for the United States catching up with the United Kingdom belongs to John Ericsson, who overcame his strained relationship with the Navy to produce the revolutionary turret-gun design for the USS Monitor. In the process, he transformed naval warfare and arguably saved the Union when the Monitor defeated the ironclad Virginia at the Battle of Hampton Roads.40
The Navy of today cannot wait for war to adapt to technological change, nor should it hope that a once-in-a-generation innovator like Ericsson will emerge to save it in its hour of need. The rate of change that AI will bring is too steep to play catch-up. The Navy must adapt quickly and creatively, in ways that play to its strengths. Time is not on the Navy’s side. But history is—if the service heeds its lessons.
1. R. John Brockman, Commodore Robert F. Stockton: Protean Man for a Protean Nation (Amherst: Cambria Press, 2009), 96–99.
2. William Conant Church, The Life of John Ericsson, Vol. I (New York: Charles Scribner’s Sons, 1902), 92–93.
3. David k. Brown, Before the Ironclad: Warship Design and Development 1815-1860 (Barnsley: Seaforth Publishing, 1990), 56, 61. Although the vulnerability of paddle wheels to disabling fire was an oft-cited critique, British experience in combat showed the risk was exaggerated. Ibid at 77.
4. John O. Sergeant, A Lecture on the Late Improvement of Steam Navigation and the Arts of Naval Warfare, (New York and London: Wiley and Putnam, 1844), 13–16.
5. At the Trafalgar meeting, Stockton commissioned Ericsson to build a screw-propeller canal boat, subsequently named the Robert F. Stockton. Whether Stockton commissioned the designs for the warship at the same time, or whether it was merely discussed, and commissioned at a later London meeting in 1839 is unclear. Brockman, Commodore Robert F. Stockton, 96–99.
6. John Ericsson, Contributions to the Centennial Exhibition (New York: John Ross & Co., 1876), 12–14.
7. Lee M. Pearson, “The ‘Princeton’ and the ‘Peacemaker’: A Study in Nineteenth-Century Naval Research and Development Procedures,” Technology and Culture 7, no. 2 (Spring, 1966): 168–69. In May 1844, the Committee on Naval Affairs of the House of Representatives issued a report on the Princeton accident, stating that with regards to Stockton’s role in building the ship, “[i]t was irregular to permit an officer unconnected with the Construction or Ordnance department to proceed with so little restraint in the building and arming of a ship of war, as was the case with regard to the Princeton.” H.R. Rep. No. 479, at 2 (1844).
8. “The U.S. Steamer Princeton” The Daily Madisonian, 8 September 1843.
9. “Deck Logs of the U.S.S. Princeton,” 28 February 1844 (National Archives, R.G. 24, Records of the Bureau of Naval Personnel, Entry 118, Logs of US Navy Ships). The most complete, contemporaneous account of the Peacemaker explosion comes from Rep. George Sykes, who witnessed the events, and described them in a letter to his sister about a week after the accident. The letter is reprinted in St. George L. Sioussat, “The Accident On Board the U.S.S. Princeton, February 28, 1844” Pennsylvania History: A Journal of Mid-Atlantic Studies 4, no. 3 (July, 1937): 161–89.
10. The Peacemaker accident also dramatically affected Tyler’s personal life. Among those killed was David Gardiner, the father of the 23-year-old debutant Julia Gardiner, to whom the 53-year-old widower Tyler had proposed marriage. Initially hesitant to accept Tyler’s proposal, Julia changed her mind following her father’s death, marrying Tyler four months following the accident, becoming the youngest first lady in U.S. history. New York World, 28 October 1888, at 17.
11. Church, The Life of John Ericsson, 140–41.
12. “Ericsson’s Petition to the Honorable the Congress of the United States,” (National Archives, R.G. 123, Court of Claims docket 13); Church, The Life of John Ericsson, 143.
13. The first wrought iron gun built for the Princeton was built in Britain by the Mersey Iron Works. Named the Oregon, the gun developed barrel cracks during test firing, which Ericsson fixed by shrinking iron bands around the trunnion. When the Peacemaker was made by the Hamersley Forge of New York, the supporting bands were welded on, instead of shrunk. Ericsson, Contributions to the Centennial Exhibition, 14. A review by the Franklin Institute following the explosion cited the welded bands as a factor in the failure of the Peacemaker. “Report on the Explosion of the Gun on board the Steam Frigate ‘Princeton’,” Journal of the Franklin Institute, Vol 8. (1844), 215. Although the historical record does not explain why the change was made from shrunken to welded bands, Church claims (without citation) that Ericsson warned Stockton to use the Oregon, rather than the Peacemaker, for the Potomac demonstrations. Church, Life of John Ericsson, 124; and Edward L. Beach, The United States Navy: A 200 Year History (Boston: Houghton Mifflin, 1986), 218. Although there is no evidence that Stockton was the source of the rumors, there is also no evidence he did anything to stop them.
14. Claude H. Hall, “Abel P. Upshur and the Navy as an Instrument of Foreign Policy,” The Virginia Magazine of History and Biography 69, no. 3 (1961): 293–95.
15. A partial list of Ericsson’s screw-propelled ships may be found at Ericsson, Contributions to the Centennial Exhibition, 17.
16. “Report of the Secretary of the Navy,” in Message from the President of the United States to the Two Houses of Congress (Washington: Beverley Tucker, 1854), 392–93 (noting the Secretary’s determination to build the six screw frigates at Navy yards, albeit with the construction of machinery contracted out); “Report of the Secretary of the Navy,” in Message from the President of the United States to the Two Houses of Congress (Washington: Cornelius Wendell, 1858), 584 (noting that only one of five screw sloops would be built by contractors); Richard Snow, Iron Dawn: The Monitor, the Merrimack, and the Civil War Battle that Changed History (New York: Scribner, 2016), 53–54 (noting of the engines of one of the screw frigates, the USS Merrimack, “[b]eyond being weak and costly, the plant was in constant conflict with the ship, thrashing at wooden bracings not sturdy enough to support it properly, and chewing up its bearings”).
17. Roger Chesneau, ed., Conway’s All the World’s Ships, 1860–1905 (New York: Mayflower Books, 1979), 116.
18. Brown, Before the Ironclad, 104–9; John Bourne, A Treatise on the Screw Propeller (London: Longman, Brown, Green & Longmans, 1852), 84–87.
19. Although launched after Rattler, the Princeton would be the first commissioned.
20. Brown, Before the Ironclad, 114–16.
21. Propeller development was also often the result of serendipity, such as when Smith accidentally broke off half of one of his original propellers, only to discover that the remaining half performed better than before the accident. Bourne, A Treatise on the Screw Propeller, 84.
22. Brown, Before the Ironclad, 122.
23. Brown, Before the Ironclad, 121–35. One of the first screw propeller warships built by the French was the Pomone, whose engines were designed by Ericsson. Church, The Life of John Ericsson, 138.
24. Government of the United Kingdom, The Navy List (London: H.M. Stationery Office, 1857), 137–82; United States Government, Register of the Commissioned and Warrant Officers of the United States Navy and Marine Corps and Reserve Officers on Active Duty (Washington: A.O.P. Nicholson, 1856), 108–9. Calculations of the percentage of Royal Navy ships exclude harbor service, packet vessels, contract mail steam vessels, and revenue vessels.
25. Government of the United Kingdom, The Navy List (London: H.M. Stationery Office, 1861), 151–211; United States Government, Register of the Commissioned and Warrant Officers of the United States Navy and Marine Corps and Reserve Officers on Active Duty (Washington, DC: 1860) 104–6.
26. Clayton M. Christensen, The Innovator’s Dilemma (New York: Harper, 1997), xviii-xx.
27. Christensen, The Innovator’s Dilemma, 125–28.
28. Christensen, xxiii–xxiv.
29. Deanna Malatesta and Craig R. Smith, “Lessons from Resource Dependence Theory for Contemporary Public and Nonprofit Management,” Public Administration Review 74, no. 1 (January/February 2014): 15.
30. This includes the Atlantic seaboard covering over 2,000 miles, plus 4,468 miles of canals, and the Mississippi River system stretching an addition 3,700 miles. T.C. Purdy, Report on the Canals of the United States (Washington: Department of the Interior, Census Office 1883), 1.
31. United States Forest Service, The Lumber Cut of the United States 1907 (Government Printing Office, 1908), 7.
32. Dan Bogart, et al., “Turnpikes, canals, and economic growth in England and Wales, 1800-1850” (Working Paper, University of California Irvine, 2017), 4.
33. The United States produced 563,755 tons of pig iron in 1850, compared to 2.25 million tons in the United Kingdom. The price of foundry pig iron in the UK in 1856–65 was 57 shillings per metric ton, compared to 103 in the United States. Peter Temin, Iron and Steel in Nineteenth-Century America (Cambridge: The MIT Press, 1964), 264; Chris Evans and Göran Rydén, “The Industrial Revolution in Iron: An Introduction” in The Industrial Revolution in Iron: The Impact of British Coal Technology in Nineteenth-Century Europe (Milton Park: Taylor & Francis, 2017), 1–14; Robert C. Allen, “International Competition in Iron and Steel, 1850-1913,” The Journal of Economic History. 39, no. 4 (December 1979): 912.
34. Lloyds, Lloyds Register of British and Foreign Shipping (London: Cox & Wyman, 1859), 61–570; Board of American Lloyds, American Lloyds Register of American and Foreign Shipping (New York: Clayton & Ferris, 1859), 454–75.
35. Ibid. The British and American Lloyds do not rate ships in an identical manner, and so some interpretation is required to compare data in the two sources. For example, the British Lloyds does not note whether ships are intended for domestic or international use but does list known destinations. Therefore, I have counted ports within the British home islands (to include Ireland during this time frame) as domestic, and all others (including imperial possessions such as Canada) as international. In contrast, the American Lloyds rates steamers as either being “sea-going” or “constructed for navigating Sounds, Lakes, and Rivers.”
36. Ibid. Brown notes that in 1848 a Parliamentary report was prepared comparing the construction and operational costs of the iron-hulled Dover and wooden-hulled Widgen. Whereas the Dover’s hull was slightly more expensive to build (£4,816 to £4,257), it was far less expensive to maintain, costing £58 per year, compared to Widgen’s £131. Brown, Before the Ironclad, 84.
37. For example, the Royal Navy tested early screw propellers by converting aging “third rates” and frigates into floating batteries, or “blockships.” Brown estimates that the cost of conversion was £44,000-74,800, compared to approximately £120,000 for a newly constructed vessel. Brown, Before the Ironclad, 124–25.
38. Instead of focusing on incorporating such technologies into 6th Generation aircraft (which may not be available until the 2030s), efforts should be made to quickly retrofit just a small fraction of the over 3,000 aircraft currently mothballed at the USAF 309th Aerospace Maintenance and Regeneration Group. Doing so could provide resources to overwhelm PLA air defenses without risk to life of U.S. pilots.
39. By 1865, the Royal Navy possessed 447 screw steamers, out of 843 total vessels (53 percent). By 1868, the United States possessed 153 ironclads and screw ships out of a total fleet of 230 (66 percent). Government of the United Kingdom, The Navy List (London: H.M. Stationery Office, 1865), 137–82; United States Government, Register Of The Commissioned And Warrant Officers Of The United States Navy And Marine Corps And Reserve Officers On Active Duty (Washington, DC: Government Printing Office, 1868) 77–81.
40. Although both the Union and Confederacy initially claimed victory in the battle, the Monitor prevented the Virginia from achieving its mission to break out from the naval blockade surrounding Norfolk. With the Monitor on station, the Virginia never again engaged the Union fleet, and would be scuttled two months following the battle. Snow, Iron Dawn, 291, 333.