Traditionally, the United States maintained a small fleet intended primarily to protect U.S. trade and interests in distant regions during peacetime and both complement the country's coastal defenses and attack a potential enemy's trade during war. However, the Civil War reversed the U.S. government's traditional strategic situation. The Union had extensive and vulnerable overseas trade interests and its opponent, the Confederacy, was almost totally reliant on imports for manufactured goods. The Confederacy posed on threat to Union ports and the Union strategy of blockading southern ports would greatly facilitate the Union's war effort. As the weaker maritime power, the Confederate Navy had to play the traditional U.S. naval role in the conflict. The protagonists' strategic positions dictated the types of ships they acquired and deployed.
Neither the Union nor the Confederacy had a large naval force at war's start and both relied on acquiring civilian craft as a short cut to building up their respective fleets. With a large merchant marine and extensive civilian and government shipyards at its disposal, the Union Navy enjoyed a significant advantage and expanded far more rapidly. Fast, oceangoing steamers were acquired quickly and their officers and crews recruited to naval service. As an expedient, the Confederacy resorted to privateering, issuing letters of marque to private individuals and companies willing to attack the Union's merchant fleet and overseas trade. Confederate leaders immediately recognized they couldn't match the Union Navy in numbers. Moreover, under international law at the time, if a blockade wasn't maintained or effective, it wasn't considered valid. So, Confederate leaders sought ironclads as one of the solutions to the Union's superior numbers and "break" the blockade by driving away the wooden-hulled blockade squadrons. Hearing of these plans and activities via its spy networks, the Union enlisted naval architects such as John Ericsson to build ironclads that would counter the Confederate ironclad threat.
Within that context, both navies' warships can be broken down into two broad categories, those built for the navies and those acquired via purchase, capture or, in the Union's case, transferred from other government agencies (Revenue Cutter Service, Army, etc). The most common warship available to both sides was the steam sloop, essentially a sailing sloop of war with steam propulsion added. Their sailing rig ranged from two-masted schooners to three-masted full rigs (square sailing rig) and they generally used a 150-400 shaft horsepower two-cylinder simple expansion steam engine. The steam engine normally provided a top speed of 5-8 knots but fuel consumption was so high that the steam engines were used sparingly, normally only during pursuit or combat. The larger sloops, particularly those built after 1861, had a top speed of ten knots on steam alone and up to fourteen knots using combined steam-sail propulsion. The screws could be removed for operating in sail alone. Armament normally consisted of one 8- or 11-inch pivot gun, two to four 32-pounder smooth bore cannon in broadside and a single rifled cannon, usually a 150-pounder. Their normal crew compliment was 65-120 men.
The Union Navy had two classes of steam sloops in service or under construction at war's start; the Hartford- and Mohican-classes. The later Ossipee and Sacremento-class steam sloops were derived from the Mohicans, with a broader beam, greater length and more powerful steam engine. The Unadilla-class steam sloops or 90-day gunboats were the first steam sloops built for Union service after the war's start. The eight Unadillas were the first to enter service and the later Kansas-class units essentially were expanded and improved Unadillas. Steam sloops were the primary naval warships the Union built for blockade duty and the Confederacy's two most successful commerce raiders, CSS Alabama and CSS Shenendoah, were steam sloops built in English shipyards. USS Kearsarge, famous for defeating the Alabama, was a Mohican-class steam sloop. The Kearsarge's captain had enhanced his ship's combat effectiveness by storing anchor chain around its engine room in a primitive form of ad hoc armor protection. Ship's captains on both sides often made such "local modifications" to their ships. More importantly, the bulk of requisitioned Union naval units consisted of commercial steam sloops armed and manned by naval crews.
The Union Navy had five larger fully-rigged Merrimack-class steam frigates at war's start. The Merrimack itself was lost with the Norfolk Naval Shipyard in 1861 and formed the basis for the Confederate ironclad CSS Virginia. However, these ships required too much draft (over 23 feet) for most of the war's naval operations and therefore served most often on trade protection. They were "two-banked" frigates carrying 40-50 guns and when built in the late 1850's, were intended to be more powerful than any potential foreign counterpart. They carried a full broadside of 24-28 9-inch Dahlgren guns and another twenty 8-inch shell guns on their upper deck, making them potentially the most powerful ships of their type afloat. Their screws could be hoisted for sailing but they proved slow (only eight knots on steam, ten knots using combined propulsion) and cumbersome in service. Nonetheless, the Royal Navy built 11 screw frigates in response to these ships. The sixth unit wasn't completed until after the war and USS Roanoke was converted into a triple-turreted monitor in 1863. However, her deep draft and poor seakeeping characteristics limited her to duty as the Hampton Roads "guard ship" until after the war, when she was scrapped.
The Union also entered the war with three paddle wheel steamers in service, USS Susquehanna, Powhatan, and Mississippi. Their shallow draft (8 feet) and powerful batteries (up to twenty 9-11 inch guns) made them exceptionally useful during the Mississippi River campaign of 1862-1863. They participated in the assault on New Orleans and Port Hudson. The Mississippi was lost at Port Hudson but the Susquehanna and Powhatan, both veterans of the Matthew Perry expedition to Japan, survived the war and served for several decades afterwards. Both sides acquired paddle-wheel steamers from civilian trade during the war, primarily for operations in and along southern coasts and rivers where their shallow draft and paddle-wheel propulsion were well suited. Most "requisitioned" paddle wheel steamers had a battery of 4-6 guns, usually 8-10-inch or 32-pounders and had a top speed of 5-9 knots. These requisitioned paddle wheel steamers were the most numerous naval units employed in the Gulf of Mexico and Western waters.
Ironclads constituted the most important and critical warships of the Civil War. By 1863, no Union commander considered it wise to operate near a major Southern port without at least one ironclad in his squadron. The Union Navy's ironclads could be broken down into two types, monitors with 1-2 armored turrets, and casemated ironclads (employed armored casemates to protect their guns, hull or propulsion systems). All the Confederate Navy's ironclads were casemated units. With the exception of USS Roanoke mentioned above, the Union's ironclads were designed to incorporate armor from the keel up, although there were several cases where ship's Capt.s added iron plates or other forms of improvised armor to their ships.
The Union built three classes of monitors during the war. USS Monitor was the first to enter service, just in time to engage CSS Virginia in the Battle of Hampton Roads. Designed specifically to engage other ironclads in coastal waters, the Monitors had a shallow draft, very low freeboard (only 18 inches) and low speed (only 6 knots in the early classes, 7-9 knots in the later ones). Armor improved as the war progressed but the Monitor's turret had eight 1-inch iron plates pressed around the turret frame and the hull had two layers of half-inch plates bolted onto 18-inch oaken planks. The hull was protected by 5-inches of iron plates bolted onto 25-inches of oak. Its armament consisted of two 11-inch smoothbore Dahlgren cannon in an armored and powered turret (2.5 turns per minute). The ten units of the follow-on Passaic-class was designed to carry two 15-inch Dahlgrens. A cannon shortage led to them carrying a single 15-inch and another gun of lesser caliber until 1865. The Passaic-class employed a number of improvements over the Monitor. The pilot house was moved to the top of the turret and speed was increased to 7 knots. The nine units of the Canonicus-class, incorporated improvements derived from the lessons learned at the April 1863 Battle of Charleston. All had twin 15-inch guns, roomier turrets to provide a higher rate of fire, more powerful engines, a higher top speed (8-9 knots) greater length and more robust turret rotation mechanisms. The last class of Union monitors built was the Onondaga-class of twin-turret monitors. Only two were completed before the war's end. These iron-hulled units carried two 15-inch and two 8-inch Dahlgrens and were the most powerful ironclads to serve in the war.
The Union also built three casemate ironclads. None were particularly successful and suffered poor seakeeping qualities. The Galena was 180 feet in length, displaced 738 tons, and carried four 9-inch Dahlgren cannon and two 100-pounder rifled cannon. Her steam engines gave her a top speed of only 8 knots. More significantly, her interlocking 3-inch armor bolted over 18-inches of oak proved completely inadequate in combat. Her crew suffered heavily at the Battle of Drewry's Bluff in 1862, forcing her removal from service. USS New Ironsides was a much more successful design, employing 4.5-inches of forged iron armor over 15-inches of oak. A larger ship with a length of 232 feet and displacing 3400 tons, she carried a more powerful broadside battery of fourteen 11-inch Dahlgrens and two 150-pounder rifled cannon. She was grossly underpowered and suffered from poor maneuverability. Her top speed was only 6 knots. Nonetheless she was the most powerful Union ironclad in terms of firepower of the war. The last of the Union's casemate ironclads, USS Keokuk, was commissioned in March 1863. Keokuk employed "sandwiched armor." That is, Keokuk had half-inch boiler iron sandwiched between two 18-inch layers of oak. Displacing 677 tons and equipped with two "stationary" turrets carrying one 11-inch Dahlgren each, Keokuk didn't do well at the Battle of Charleston, sinking the next day from the damage received in the battle.
The Confederacy built 22 ironclads during the war. All were underpowered, using whatever steam machinery was available and under-armored in comparison to their Union counterparts. Originally intended as "blockade breakers," they were seen at the end as critical to the South's harbor defenses. The first, the CSS Virginia, was built on the damaged hull of the former Union steam frigate, USS Merrimack. The basic hull and machinery were retained, as were some elements of the battery. The wooden hull was retained but covered over by a single 2-inch iron plate. The above-deck casemate that housed the pilot house and cannon was built upon an oak frame, angled at 35 degrees and used 25-inches of oaken planks covered by two 2-inch iron plates that extended to a foot below the waterline. An iron-ram was installed in the bow. Armament consisted of six 9-inch Dahlgren smoothbore cannons and two imported Brooke 6.4-inch rifled cannon in broadside and one 7-inch Brooke rifled cannon in each the bow and stern. The Virginia's 23-foot draft and poor maneuverability limited her operations to Hampton Roads' most open reaches but that was seen as sufficient to break the blockade. CSS Virginia provided the basic framework for all subsequent Confederate ironclads.
Three basic classes emerged, the Richmond-class (basically a scaled-down Virginia), the more heavily armored Charleston-class and the smaller Albemarle-class. The six units of the Richmond-class measured 150-174 feet in length, had a draft of 12-14 feet and had a top speed of 4-7 knots. Propulsion was the weakest element of all Confederate ironclads. None had a top speed of over 7 knots and most were lucky to reach 5. Their armor extended over the hull to reduce one of the vulnerabilities noted during the Monitor-Virginia engagement. The three Charleston-class units differed only in having a greater length and more armor. The four Albemarle-class units were generally smaller (130 feet in length), more lightly armed (two 6.4-inch Brooke Rifled cannon) and served only in the upper reaches of the James River. The so-called Tennessee-class actually consisted of a series of vessels, each of a unique design with casemate construction being their only common feature. Armor protection essentially was standardized at two layers of 2-inch rolled iron plate or an equivalent thickness in "railroad iron." The latter was not considered as effective as rolled plate but had to suffice since there wasn't enough plate to meet requirements, particularly in the West. After CSS Atlanta was lost to Union guns penetrating her 4-inch armor, an additional 2-inch plate was added in the three units of the Charleston-class. The Charleston-class ironclad, CSS Virginia II, built in late 1863, incorporated a 4th layer of two-inch plates in some areas, making it the most heavily armored of the Confederate ironclads. Efforts to produce 3-inch plates proved futile.
After the engagement with the Monitor, Confederate authorities preferred to equip their ironclads with rifles. The 6.4-inch Brooke rifle was the standard broadside gun and the 7-inch Brooke cannon was generally placed in the bow and stern positions. However, 32-pound smoothbores and the 8-inch Dahlgren smoothbores were used when rifled cannon were not available (e.g. CSS Arkansas, CSS Manassas & CSS Savannah). The Richmond-class units carried four 6.4 inch Brooke Rifles in broadside and an 8-inch Brooke rifle in the bow and stern positions. The CSS Charleston carried a 9-inch Dahlgren smoothbore in place of the Brooke rifle in the bow and stern positions.
Confederate forces also employed requisitioned paddle wheel steamers and Confederate privateers included a sailing brig among their numbers. In general, however, the South's limited industrial base and small maritime related population limited its naval options. The Union Navy on the other hand, expanded from a force of less than 200 ships in 1860 to over 1,000 vessels of all types by April 1865. The Civil War transformed the United States, albeit only temporarily, from a backwater to a major naval power. The South's commerce raiders severely depleted the Union's merchant marine and whaling fleet but otherwise, the Union Navy's blockade had a decisive impact on the war. Unable to export its agricultural products for cash and import more than a limited amount of vital war supplies, the Confederacy's military forces declined in capability as the war progressed. Unfortunately, the Union Navy's need to focus on shallow-water and coastal craft inhibited European interest in the lessons learned from its operations and provided little impetus for the United States to develop an ocean-going fleet until later in the century. Carl Otis Schuster
Canney, Donald, L. Lincoln's Navy; The Ships, Men and Organization, 1861-65. U.S. Naval Institute: Annapolis, 1998; Konstam, Angus. Confederate Ironclad 1861–1865. Ospey Publishing: London, 2001; Konstam, Angus. Confederate Raider 1861–1865. Osprey Publishing: London, 2003.
Carl Otis Schuster