The Strategic Context of the Naval War


During the Civil War, the US Navy harnessed revolutionary technologies and designs, and pioneered extensive joint operations with the Army along the Confederacy’s shores and on its rivers. The naval forces on both sides, especially on the Union side, affected the trajectory of the conflict, and helped determine its length.

The war took place during a time of dramatic changes in technology, and it marked a milestone in the character of naval warfare. Before the war, wooden sailing ships firing solid shot from iron guns were giving way to the first steam-powered, propeller-driven iron warships firing explosive shells from increasingly large rifled guns.

The best known example of this revolution was the duel between the ironclads CSS Virginia and USS Monitor on 9 March 1862 in Hampton Roads, Virginia. However, the battle the day before was the real watershed, marking the supremacy of iron over wooden warships. On 8 March 1862, the CSS Virginia (rebuilt on the hull of the Union screw frigate Merrimack) sank two wooden Union warships in a single day, inflicting on the US Navy its worst defeat since its founding in 1775. Wooden warships did not become immediately obsolete, nor did armoured warship become the new universal standard, but the Battles of Hampton Roads demonstrated the direction of change. Change was manifested in many other ways, such as the shift in the balance of relative power between warships and coastal defences.

From the beginning, the Confederacy had to concede control of the sea, as the much weaker naval power. The Confederacy embraced new innovations, such as sea-mines, torpedo boats and submarines, to try to gain an advantage. However, these novel weapons could not be produced in sufficient numbers to affect the overall balance of sea power and remained at a primitive stage of development.

In both the American Revolution and the War of 1812, the small US Navy had avoided fleet engagements with its powerful enemy and relied on attacking British commercial shipping. The British countered by attempting to blockade the American coast, interfering with trade and preventing potential commerce raiders from putting out to sea. The stronger navy enforced a blockade, and the weaker naval power turned to commerce raiding. This pattern recurred in the Civil War; the stronger Union Navy applied a blockade, and the weaker Confederates turned to commerce raiding. In addition to the blockade, the US Navy played a vital role on the Western rivers and conducted a determined but only partially successful, pursuit of Confederate commerce raiders.

The US Navy in 1861

In 1861 the US Navy had 90 vessels listed on its Register of Ships, of which only 42 were capable of active service, and most of those were dispersed on stations from Brazil to China. Soon after his inauguration, President Abraham Lincoln asked the Secretary of the Navy, Gideon Welles, what naval force was available in case of war. Welles named only 12 warships that could be put immediately into service. This was not a Navy capable of commanding the Southern coastline by blockade, pursuing commerce raiders, attacking enemy fortifications and ports or fighting on the Western rivers.

Nevertheless, the outbreak of the Civil War coincided with technological innovations that had a dramatic impact on naval warfare. Among these innovations were the powerful screw propeller, increasingly efficient steam engines, rifled and banded naval guns with greater range and accuracy, and exploding ordnance. In response to the emergence of these new technologies, the US Navy built 24 major new vessels in the decade before the outbreak of war. This was the country’s largest peacetime naval expansion since the Naval Act of 1816. Even though the Navy of 1861 was small, it contained a high proportion of modern, date warships.

The first ships of this dramatic expansion were the five River-class screw-driven frigates, named USS Merrimack, USS Wabash, USS Minnesota, USS Roanoke, and USS Colorado. At the same time a sixth frigate, the USS Niagara, was launched to a novel design, long with sharper lines and mounting fewer guns. They looked superficially like the sailing frigates of earlier years. However, they were steam-powered and propeller-driven and boasted an impressive armament of advanced guns. When the USS Merrimack visited English ports in 1856-1857, her powerful battery persuaded the British to launch a new class of steam warships.

The Southern states complained that the new steam frigates were t0o large to operate in shallow Southern ports. In 1856, Secretary of the Navy James C Dobbin therefore urged the construction of another new class of warships: smaller, shallower-draft steam sloops. These were the first US Navy warships to be driven by twin screws. These City-class warships were named the USS Hartford, USS Richmond, USS Brooklyn, USS Pensacola, and USS Lancaster. Launched in 1858, the USS Hartford drew only 18 feet of water, allowing her and her sister ships to enter most Southern ports where the bigger steam frigates could not pass. During the conflict, vessels like the USS Hartford, USS Richmond and USS Brooklyn, were able to steam up the Mississippi as far as Vicksburg and into Mobile Bay. This was an unanticipated outcome of Southern demands for this kind of vessel.

In 1858 a third type of new steam warships was authorised by Congress. The first of these Indian-class screw steamers was the USS Mohican, launched in 1859. The others were the USS Pawnee, USS Wyoming, USS Iroquois, USS Dacotah, USS Seminole, and USS Narragansett. These small ships carried sailing masts and spars, but their sail pattern was much reduced. These were the first American warships to be classified as steam warships rather than sailing vessels with auxiliary steam power.

Between 1854 and 1859, the US Congress authorised funds for three new classes of steam-powered, propeller-driven warships, as well as other ships, numbering 24 vessels in all. These appropriations enlarged and modernised the fleet in a way that made the US Navy more prepared for war in 1861 than for any previous war.

Obstacles to the Union Blockade

President Abraham Lincoln’s declaration of a blockade on 19 April 1861, only four days after the surrender of Fort Sumter, was the administration’s first important strategic decision. From the outset there were two major obstacles to overcome.

Declaration of a blockade was an act of war, and Lincoln’s pronouncement therefore implied the granting of belligerent status to the Confederacy. The President insisted that the Confederacy had no legal standing and the conflict was a rebellion against the government. However, the blockade implied that the Confederacy had some status as an independent entity. Lincoln and Secretary of State, William H Seward partially evaded this implication by announcing that domestic unrest in Southern ports required their closure to commerce. The European powers were not deceived by this attempted subterfuge. In addition, the closure of certain ports alone did not justify patrols beyond the immediate coastline by Union warships to stop blockade violators. The Union government was forced to concede that the use of the term “blockade” had undesirable implications about the legal status of the Confederacy.

Lincoln’s declaration of the blockade was one factor in the British decision to grant belligerent status (although not formal recognition of independence) to the Confederacy. Initially, this recognition was seen as a threat but it worked to the Union advantage since it barred warships and privateers of both sides from British ports. The British stretched some terms of neutrality almost to breaking point during the war, but Confederate commerce raiders remained barred from bringing their prizes into British ports (including the West Indies) and this severely limited their effectiveness.

According to international law, neutral powers did not have to respect a blockade unless the blockading power established a naval presence off every port that was declared to be under blockade. Declaring that a coast was blockaded was insufficient; the blockade had to be proven to be real and effective. The Confederacy had a coastline of about 3,550 miles served by 189 harbours, inlets, and navigable rivers. The US Navy had too few warships to be physically present at every point. Moreover, at most ports a single vessel was inadequate; some would require a dozen ships or more to make even a pretence of a continuous and effective force. In spite of its initial numerical superiority, the US Navy’s had to expand rapidly to many times its pre-war strength.

Most of the new blockading ships were converted merchantmen. Some steam merchant ships could be converted easily by strengthening the decks to sustain the weight of naval ordnance and by constructing a secure magazine below the water line. These conversions were made at various naval yards. At the Brooklyn Navy Yard alone, some 190 ships were successfully refitted. As an exceptional case, workers transformed the merchant steamer Monticello into a warship in less than 24 hours.

Seizing Bases of Operations

The US Navy was able to expand quickly because of its industrial capacity, but crewing and maintaining that force off the hostile coastline for four years was extremely challenging. Most ships were steam powered fuelled by coal. Keeping them at their blockade stations required the seizure of bases along the coast for refuelling and resupply. One of the first recommendations of the Blockade Strategy Board, established by Secretary of the Navy Gideon Welles at the start of the war, was to acquire two secure coaling stations on the South Atlantic coast. The board recommended Bull’s Bay, South Carolina, and Fernandina, Florida, but after further consideration, the first objective was set as Port Royal, South Carolina.

Port Royal lay between Charleston and Savannah, and could support blockading squadrons off both of those ports. Port Royal had an enormous roadstead, large enough to accommodate the entire Union Navy. Its offshore islands were cut off from the mainland by swamps, protecting the Union base from overland attack.

Flag Officer Samuel Francis Du Pont chaired the Blockade Strategy Board, and he commanded the fleet that conducted the first major naval operation to capture Port Royal. He led a huge armada of 75 ships, the largest naval force ever assembled under the American flag. A terrible storm off Cape Hatteras scattered the fleet but eventually most of the ships arrived at their target. On 7 November 1861, Du Pont led his warship squadron into Port Royal Sound.

Conventional wisdom stated that stationary guns in forts outclassed guns aboard ships. Ships were made of wood, and forts were constructed of brick and stone. Forts could mount larger guns and access to unlimited supplies of ammunition. Forts could be repaired easily and not sink. During the Fort Sumter crisis, the New York Tribune declared the accepted view that “ships are no match for land batteries.” This assumption did not reflect recent changes in naval technology. Unlike sailing ships, Du Pont’s wooden steamers could remain in motion while firing and they could manoeuvre independently of the wind. Their modern naval guns were larger, more accurate and had longer range than heretofore. They outclassed the armament of the Confederate Fort Walker and Fort Beauregard, guarding Port Royal. These two forts were not modern masonry structures but log-and-dirt fortresses recently built and armed mainly with older, smaller artillery pieces.

Du Pont attacked Fort Walker, first. After three passes, the Union gunners had disabled most of the fort’s guns, and the defenders were running short of ammunition. Accepting inevitable defeat, the garrison abandoned the fort, and the defenders of Fort Beauregard followed soon afterwards. Du Pont’s destruction of Fort Walker demonstrated that a squadron of modern steam warships was more than a match for existing coastal fortifications.

The victory at Port Royal had several important consequences. Psychologically, the news heartened the Northern population after the embarrassment of defeat at Bull Run in the summer. Strategically, it provided the base essential to the blockade of Charleston and Savannah. Until the end of the war, only Hampton Roads surpassed Port Royal in importance as a naval base on the enemy coast. The US Navy established a base at Key West to control the coasts of Florida. The early capture of Ship Island, near the mouth of the Mississippi River, provided a base for operations in the Gulf of Mexico.

The loss of Port Royal affected Confederate strategy. General Robert E Lee, President Jefferson Davis’ military adviser, was sent to South Carolina to report on the coastal defences. Lee concluded that the superior size of the US Navy, its mobility, and its heavy guns meant that the Confederates could not defend the entire coastline. He recommended the defence of a small number of essential and defensible sites, and the abandonment of peripheral ports. The Confederacy energetically defended Galveston, Texas; New Orleans, Louisiana; Mobile, Alabama; Savannah, Georgia; Charleston, South Carolina; and Wilmington, North Carolina. The rest of the Confederate coast was weakly defended and many points were occupied by Union forces supplied and maintained by sea.

Assessing the Blockade’s Effectiveness

The acquisition of bases on the Confederate coasts made the blockade possible, but it remained a challenging and thankless task. The general pattern of trade was for conventional cargo vessels to bring their goods from Europe to a neutral port such as St George in Bermuda, Nassau in the Bahamas, or Havana in Cuba. Their cargoes were transferred onto low, fast blockade runners. Blockade runners, were usually unarmed, and they typically attempted to dash into a blockaded port under cover of night. Blacked out and painted dark gray, they sought to evade Union warships without being sighted. If they were spotted, they tried to outrun their pursuers. After unloading, they would escape again to sea, carrying cargoes of cotton or other products.

It was very difficult to catch or even spot a well-commanded blockade runner. Most ships that tried to run the blockade were successful; however, relatively few ships took the risk. In 1860, some 20,000 ships had entered or left Southern ports, but during the war, that number dropped to only 2,000 ships per year. Cotton exports fell from just under 3 million bales in 1960 to just over 50,000 in 1861, 2 per cent of pre-war trade.

It is difficult to make an exact evaluation of the effectiveness of the Union blockade. The South managed to import munitions and commodities essential to its economy and war effort. This included 400,000 rifles, 3 million pounds of lead, and more than 2.2 million pounds of saltpetre for manufacturing gunpowder. Blockade runners supplied much of the military requirement for arms, bullets, and powder.  However, the blockade increasingly eroded the Southern economy, and contributed to inflation and war weariness among civilians and soldiers. It certainly eroded the Confederate war effort with increasing impact. While the blockade was never completely effective, it did constrict and suffocate the Southern economy. The Union could perhaps have won the war without the blockade, but the war would certainly have lasted longer and been more costly.

Action on the Western Rivers

After the blockade, the second most important area of operations for the US Navy was on the Western rivers between the Appalachian Mountains and the Mississippi River. While the rivers in the East ran eastwards to the Atlantic, and acted as barriers to Union advances overland, the Mississippi flowed south to north and pierced the Confederacy. The Tennessee and the Cumberland flowed south to north into the Ohio and thence to the Mississippi and provided similar routes to the hinterland. As a result, the rivers could provide avenues for Union advances, piercing the Confederacy. Whichever side commanded the Western rivers held a tremendous strategic advantage.

The Union industrial base allowed it to produce more and better warships for the river war. Even before the ironclad CSS Virginia was launched or the USS Monitor was built, the Union was constructing a flotilla of small river gunboats, protected by iron or other armour and powerfully armed. They were designed to navigate the relatively shallow waters of the inland rivers.

The Confederacy attempted to build armoured gunboats for the Western rivers and laid down two large ironclads at New Orleans and two more at Memphis. The Confederacy’s inferior industrial base and the early loss of these cities hindered the effort. Only one of these four ironclads was completed: the CSS Arkansas. The Confederates were forced to depend on riverside fortifications to prevent the progress of the Union armies along the rivers. The initial line of defence, from Island Number Ten on the Mississippi to Cumberland Gap, tracked the Tennessee-Kentucky border. The first major Union campaign in the West was led by Union gunboats attacking the Confederate fortifications.

The Union had no protocols for joint operations of the Army and Navy but quickly gained experience on the coastline and on the inland rivers. After some early confusion, the generals and admirals learned to work effectively together. The Army took strategic control of operations in the Western theatre, and the US Navy exercised tactical command of their ships and squadrons. This arrangement was informal and depended on willing cooperation rather than an explicit statement of priority of command.

Early Union Victories in the West

The first major test of joint operations came at Fort Henry on the Tennessee River. The army commander Ulysses S Grant, in his first significant operation, and Flag Officer Andrew Hull Foote combined to capture this key position. Foote’s gunboat flotilla transported Grant’s troops to a point above Fort Henry, and then fired on the fort as the soldiers advanced overland. The Confederate position was vulnerable and was evacuated by the infantry, leaving the fort to be defended by artillery alone. Foote’s four ironclads overwhelmed Fort Henry’s batteries, and the fort capitulated before the army could arrive. The gunboats then steamed past the fort, seven miles upriver to destroy the railroad bridge over the Tennessee River, cutting a vital east-west link for the Confederate.

The next objective was Fort Donelson on the Cumberland River, a day’s march east of Henry and the keystone of Confederate defence in the West. Foote’s gunboats found Fort Donelson, well placed on higher ground above the river, a formidable obstacle. Grant’s army marched to besiege the fort on the land side and compelled the surrender of the fort on 16 February 1862. This victory forced the Confederates to evacuate Kentucky, and much of Tennessee

Cooperation by the Union Army and Navy was also efficient in the operations against Island Number Ten on the Mississippi River. The island held the principal Confederate defensive position on the Mississippi. Protected by impassable swamps to the east and the river to the west, the fort was secure from overland attack except from the south. Union forces could only attack the fort from the south only if the Navy could pass the Confederate guns and carry Union troops across the river to the island.  On 4 April 1862, Commander Henry Walke, captain of the ironclad USSS Carondelet, volunteered to run his ship past the enemy batteries. Foote was sceptical but gave his permission. Despite a harrowing journey, Walke made it, and his example inspired a second run by the USS Pittsburg two nights later. The two gunboats then conveyed John Pope’s army across the river into the Confederate rear for a near bloodless victory. This was a model of cooperation which was repeated throughout the war.

From New Orleans to Vicksburg

At the same time, 500 miles further south, Union Flag Officer David Glasgow Farragut ran his ocean-going warships up the Mississippi from the Gulf of Mexico. He passed easily by the two forts on the lower Mississippi that protected the city of New Orleans. These fortifications were not hastily erected dirt-and-log forts like Port Royal or Island Number Ten, but large masonry structures built before the war to the most modern designs. Between them, Fort Jackson on the western bank and Fort St Philip on the eastern bank mounted 128 heavy guns. On 24 April 1862, Farragut’s wooden warships steamed through an opening cut through a log-and-chain boom and fired on the forts. Fourteen vessels successfully ran the gauntlet against the current, and crushed the small squadron of Confederate vessels that emerged to contest their passage. Farragut reached New Orleans and demanded the city’s surrender. New Orleans was the largest city and most important seaport in the Confederacy. Its early fall and control of the outlets of the Mississippi inflicted a severe blow on the Confederacy.

Having taken command of the lower Mississippi, Farragut steamed upriver past Baton Rouge to Vicksburg but his unsupported ships could not capture the city. Eventual Union success at Vicksburg required the cooperation of the Union Army and Navy. In April 1863, Grant asked Flag Officer David Dixon Porter to run his naval squadron past the Vicksburg batteries. Porter’s gunboats steamed through destructive gunfire on 16 April and later carried Grant’s army across the river from the western to the eastern bank. Grant marched boldly into Mississippi, won several battles, and imposed a 47-day siege of Vicksburg. Vicksburg fell on 4 July.

Cooperation was essential in the efforts to close the important Confederate ports along the Atlantic coast. Charleston, Mobile, and Wilmington required combined operations by the army and navy. The campaign against Charleston lasted more than two years, but the city fell only when threatened by an army marching from Georgia in February 1865. The assault on Mobile, Alabama, was also a joint operation, although the city had been closed as a haven for blockade runners by Farragut’s fleet on 5 August 1864.The first joint Union assault on Fort Fisher, guarding the port of Wilmington, North Carolina, failed ignominiously in December 1864 but a second better-coordinated attempt in January 1865, was successful.

Raiding on the High Seas

The third element of the Union naval effort was the pursuit of Confederate commerce raiders. The Confederate government quickly issued letters of marque to privateers, authorising them to attack US merchant shipping. The experiment failed when the Union blockade and the British declaration of neutrality closed most ports where prizes could be sent for adjudication and condemnation. Without the profit motive, privateering lost its appeal.

Commerce raiding then fell to Confederate Navy warships built or purchased in England and manned by international crews. The most successful was the CSS Alabama, commanded by Captain Raphael Semmes. Between July 1862 and June 1864 Semmes captured and burned 64 Union merchant ships and sank a Union warship, the USS Hatteras. Northern trade was disturbed by these so called “pirates”. The New York Chamber of Commerce pressed for convoys to protect American shipping but the idea was rejected because the allocation of escorting war ships would weaken the blockade.

The strategy adopted was to send fast, well-armed ships to hunt down the commerce raiders. This strategy was frustratingly ineffectual, although Union warships eliminated two of the most notorious raiders in 1864. The CSS Alabama was sunk off Cherbourg, France, on 19 June 1864 by the USS Kearsarge, commanded by Captain John Winslow. In October the USS Wachusett, under Commander Napoleon Collins, captured the CSS Florida in the neutral port of Bahia, Brazil. The last of the Confederate raiders was Commander James I Waddell’s CSS Shenandoah. After savaging the US Pacific whaling fleet in the spring and summer of 1865, Waddell only learned that the war had ended in May 1865. Fearing reprisal for the captures he had made after the end of hostilities, he sailed the CSS Shenandoah to England, where her flag was hauled down in November 1865 as the last Confederate surrender of the war.


The Union did not win the Civil War because of its naval superiority, but it was an essential element in achieving final victory. The blockade created shortages and hardship within the Confederacy and cut off the putative nation from help from the rest of the world. The Navy supported the advance in the Western theatre that split the Confederacy. Despite their endeavours, Confederate commerce raiders never threatened Union naval superiority and did not change the outcome of the war. Despite their many innovations and many successful engagements, the Confederacy never broke Union superiority at sea or on the inland rivers.

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