By LT Jason Lancaster, USN
Throughout history, maritime nations have used naval blockades to wreck the economies of their adversaries and bend them to their will. However, the impact of blockade in history has been overstated. Throughout history, blockade has been a part of military success, but it has never been the primary key to victory. Most successful blockades enabled land campaigns to succeed but would not have won wars on their own. Blockades are a politico-economic form of warfare that can quite often have unexpected political results. Modern calls to defeat China solely through an “easy and bloodless” naval blockade understate the physical difficulties and political challenges of a successful blockade, ignore that successful blockades support events ashore, and that blockades have not been successful as standalone campaigns.
Legal Definitions of Blockade
The San Remo Manual on International Law applicable to Armed Conflicts at Sea includes the requirements for a blockade. It must be announced, and all neutral and belligerent states should be notified of the blockade. It must be effectively maintained by a force as close as is required to be effective. It must not bar access to the ports and coast of a neutral state. It must be applied impartially to vessels of all states.
A blockade is not lawful if it has the sole purpose of starving the civilian population or denying it objects essential for survival, or the damage to the civilian population outweighs the military advantage of the blockade. The blockading belligerent shall allow the passage of medical supplies for the civilian population or for sick and wounded members of the armed forces.1 These requirements are designed to allow maritime states to conduct operations while minimizing the suffering of the civilian population of belligerents.
Quarantine is not a blockade. According to the Navy Commander’s Handbook on Operational Law, “the goal of quarantine is de-escalation and a return to the status quo ante.” The goal of a blockade is “denial and degradation of an enemy’s capability.”2
The British Blockade of Napoleonic and Revolutionary France
While some have argued that British blockades were the reason for victory over Napoleon, the blockades were not the root of victory. Even though they caused economic hardship it was not severe enough to force France to make a lasting peace. 20 years of blockade took its toll on cities like Bordeaux that relied on foreign trade and industries set up around imports like refining sugar, but the loss of such trade did not cause France to surrender. 20 years of bloody war from the Russian Steppes to the coast of Portugal caused the French empire to collapse after repeated military defeats ashore.
From 1793 until 1802 and between 1804 and 1814, Great Britain conducted a close naval blockade of France and her allies. Throughout the wars of the 18th century Britain had refined the techniques and logistics of supporting a fleet on a hostile shore for sustained periods of time. Despite the idea that the primary purpose of the blockade was to strangle French commerce, the real purpose of the blockade was to prevent the French from invading Britain or Ireland. Despite the arduous blockade, the French twice managed to land forces in Britain and Ireland during the war. The blockade did limit the size and effectiveness of the landings. Humorously, the French invaders that landed at Fishguard, Wales surrendered to the local women who had come to look at the strange invaders.
Throughout the war, the close blockade of Brest was hotly debated. Was it better for ships to be beaten and battered off the stormy Biscay coast, or to maintain the fleet in port in expectation for the French to come out? Ships were lost in wrecks or damaged sufficiently to be sent back to British dockyards for repairs. These losses impacted the overall strength of the blockading force if the French did come out.3 Parallels can be drawn between the surface fleet today and the Royal Navy of 1805. The dockyards were full of ships desperately needing refit after years at sea, but the number of qualified dockyard workers had dwindled in both private and public dockyards. Shortages of skilled dockyard workers meant that new construction took longer than expected. HMS Royal Sovereign, Admiral Collingwood’s flagship at Trafalgar, was still in construction after 12 years, almost 3 years longer than normal for a first rate ship of the line.4
The British blockade had an economic impact on Europe, but in some industries the impact was to preserve the traditional production method and delay the introduction of the new mechanized production methods used in Great Britain. The British blockade and the French Berlin Decrees banning trade between the continent and Great Britain certainly affected trade, but only seldom did it cause production to cease entirely. There were shortages of raw materials like cotton, but the cotton mills only went idle for a few months in 1808. The price was sometimes 2-4 times as high as that paid in Britain. From 1790 until 1810, French cotton consumption increased threefold while in Britain consumption increased fourfold.5
The blockade had unexpected political repercussions for Great Britain. The British blockade of France and her allies helped cause a war with Denmark in 1801 and the United States in 1812. Many ships from occupied places like the Netherlands ended up registering their vessels in neutral nations like Denmark and Sweden to continue trading. According to international law goods that were not contraband in neutral vessels could not be impeded. However, neutral goods such as hemp, pitch, tar, and pine logs were used to build and support naval vessels. Wheat was a neutral good but its dual use could make bread for the average French citizen or the citizen soldier. Britain argued that when the entire nation was in arms, was there a difference? Annoyed at British interference in their trade, Denmark, Sweden, Prussia, and Russia re-created the League of Armed Neutrality. Britain sent a fleet to Copenhagen, where Admiral Nelson fought a bloody battle with the Danes and persuaded them to surrender the remainder of the fleet. This combined with the death of Tsar Paul ended the League and its threat to the blockade.
In 1812, the United States declared war on Great Britain over the issues of free trade and Sailors’ rights. Many American citizens had either moved from Great Britain or could have been considered British subjects because of when they were born in America. The Royal Navy, perennially short of Sailors, impressed them from merchant ships. To a nation fighting for its life, often times alone, the nationality of a Sailor might matter little, especially since the British government believed that subjects could not change their nationality and had “an inalienable right to their service.”6 In 1807, the HMS Leopard stopped and searched the warship USS Chesapeake, a U.S. naval vessel for deserters, took four and hung one of them. It was a step too far. President Thomas Jefferson stated of the affair, “Never since the Battle of Lexington have I seen this country in such a state of exasperation as at present, and even that did not produce such unanimity.” While this incident did not cause the United States to go to war, it played a role following continued British harassment of American merchant ships.
From 1805-1813 the U.S. and Britain negotiated over the meaning of neutral shipping. Despite these negotiations, by 1806 120 U.S.-flagged vessels had been seized by the Royal Navy. The British position insisted that American vessels must carry non-American goods to an American port, unload them, pay duties, reload them, and then they were free to transship them to any country. The U.S. position was that as a neutral nation they had the right to ship any goods anywhere.7
In 1806, the U.S. also challenged British ideas of what constituted a blockaded port. American diplomats challenged the idea that the entire coastline could be blockaded by proclamation, but rather that warships had to create, “an evident danger in entering.”8 The U.S. Congress responded to British and French declarations of blockade against each other with an embargo on some British manufactured goods in the expectation that economic policy might force the British to accede to American demands.9 The twin wounds to trade and national honor through impressment eventually meant that the U.S. preferred to fight than continue to submit to such injustices.
The British blockade hampered but never destroyed French trade. It made enemies of neutral nations, and did not expedite victory. Despite continued victory at sea, the Napoleonic Wars demonstrated that while a maritime power may contain a continental power, in total war a continental power must be defeated ashore.
Union Blockade of the Confederate States
Interestingly, if Britain would have acquiesced to American policy on blockade, then the Union blockade of the Confederacy may never have been legal. Despite the Union blockading the ports of the South, the Confederacy maintained open ports through almost the entire war. While the South suffered ever increasing shortages, blockade runners continued to supply the Confederate States and only the dominance of the northern armies compelled the South to capitulate.
The Union Navy began the war with 90 ships, including 40 steam vessels and 50 sailing ships. Not all of those ships were ready for war. Some were in the naval dockyards, some were stationed across the globe in California, the Mediterranean, Asia, and Brazil to protect tradeVessels stationed overseas would take up to six months to return to the U.S.10 At the outbreak of war, there were only three vessels ready for war on the Atlantic coast. It would take time for the Union Navy to marshal the forces required to conduct an effective blockade of a 3,500 mile coastline.
The Confederate and British governments did not believe that the Union Navy could successfully blockade the entire Confederate coast. However, the Union Blockade Strategy Board looked at the problem differently. Instead of worrying about the entire coastline, the Strategy Board broke the required blockade down to major ports with transport connections to the rest of the country. This drastically reduced the amount of coastline that required blockading. The Strategy Board utilized the United States Coast Survey’s records to examine the inlets, waterways, and ports of the South and decided that the primary ports of entry to blockade were Richmond, Norfolk, Wilmington, Charleston, Savannah, Mobile, New Orleans, and Galveston. The James and Elizabeth River channels leading to Richmond and Norfolk were blocked by Fortress Monroe and began the war well-blockaded. The remainder of the ports required blockading squadrons.
The initial organization of the Union blockading squadron consisted of one squadron blockading the Confederate coast from the Virginia Capes to Key West. This was later divided into North and South Atlantic Blockading Squadrons. The North Atlantic Blockading Squadron was responsible for the blockade between the Virginia Capes and the border between North and South Carolina. The South Atlantic Blockading Squadron was responsible for the blockade from the North and South Carolina border to Key West. In the Gulf of Mexico there was the Gulf Blockading Squadron which was also subdivided between east and west; the Eastern Blockading squadron watching the port of Mobile and the Western blockading squadron watching the port of Galveston and the Texas coast.
Ironically, the rights that the U.S. had gone to war with Great Britain over during the Napoleonic Wars were abandoned when the northern states declared their blockade of Confederate ports. The Trent affair almost brought Great Britain into the war against the north. In November 1861, two Confederate diplomats were traveling to London aboard a British flagged mail packet, the Trent. The ship was then forcibly stopped and searched by a Union frigate. Despite the protestations of the Trent’s captain, the two Confederate diplomats were taken into custody by the North and detained at Fort Warren, Massachusetts. The British government and press were outraged by the insult to their flag and international law. The two officials were released because the British government demanded their return and began some military preparations.11
While the blockade grew ever more effective, it was never entirely effective. Throughout the second half of 1864 the port of Wilmington received 3.5 million pounds of meat, 1.5 million pounds of lead, 2 million pounds of saltpeter, 500,000 pairs of shoes, 300,000 blankets, 50,000 rifles, and 43 cannon. The Army of Northern Virginia and the Army of Tennessee received new uniforms and equipment.12 This does not mean that the blockade did not cause shortages amongst the population or the army, but that as an offensive strategy blockade alone would never defeat the South.
The only effective way the North closed Confederate ports was by physically capturing the port or destroying the fortifications and ships defending the port and occupying inland waters. Savannah was not captured until December 1864 when General Sherman took the city from the landward side. The South Atlantic Blockading Squadron had supported the northern army as it bombarded Fort Pulaski into submission. With the mouth of the Savannah River closed, Savannah lost its appeal as a blockade running destination. Likewise, the port of Mobile was not captured by Admiral Farragut; however his capture of Fort Morgan and the CSS Tennessee meant that blockade runners could not reach Mobile. Oftentimes, northern efforts to close a port simply shifted blockade running to another port. The Union offensive against Charleston in 1863 shifted blockade running to the port of Wilmington which because of the geography was even more difficult for the northern fleet to blockade than Charleston.
A blockade of China would be an immense undertaking. Chokepoints like the Malacca, Sunda, and Lombok Straits would all have to be guarded. However, the Law of the Sea recognizes a 200 NM Economic Exclusion Zone (EEZ). Neutral nations’ EEZ must be respected by combatant nations. To effectively police the chokepoints of maritime Asia, Malaysia and Indonesia would have to support the U.S. position. But neither of them are U.S. treaty allies and it is a major planning assumption that they would automatically support the U.S. side in a conflict. China would certainly exert great amounts of pressure on those states to remain neutral.
An average of 52 oil tankers transit the Malacca Strait a day, and the sheer number of possible boardings and prize crews could rapidly overwhelm the combat forces enforcing the blockade.13 A more effective means of blockading China would be a massive mining campaign. During World War II the British flew 20,000 minelaying sorties in the Atlantic Theater. These sorties sank 683 Axis ships while losing 450 aircraft. Only 150 Axis ships were sank by British surface and subsurface vessels. In 1945, the U.S. Army Air Corps helped isolate Japan from the rest of the world, starving Japan of resources.14 Despite the historical successes, the U.S. has not kept pace with the rapid technological changes in mine technology. Today, the bulk of U.S. mines are air-dropped, but the U.S. would have difficulty sewing air-dropped minefields in the face of the PLAAF and Chinese air defenses.
Throughout history blockade has been used as a strategy to deny adversaries foreign trade and prevent enemy warships from going to sea. However, neither blockade mentioned solely won the war. Troops ashore decisively defeated enemy armies and seized territory to win those wars. A “bloodless distant blockade” is not a magical panacea to bend China to U.S. will. A blockade of either country will stress U.S. resources to the limit and carries unknown diplomatic risks. It has not worked in the past, and will continue to fail as a standalone strategy in the future. It is an effective aid to victory, but no secret weapon.
LT Jason Lancaster is an alumnus of Mary Washington College and has an M.A. from the University of Tulsa. He is currently serving as the N8 Tactical Development Officer at Commander, Destroyer Squadron 26. The above views are his own and do not reflect the position of the Navy or Department of Defense.
- San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 1994.
- S. Navy Commander’s Operational Law Handbook NWP 1-14M, 2007.
- National Research Council. 2001. Naval Mine Warfare: Operational and Technical Challenges for Naval Forces. Washington, DC: The National Academies Press. https://doi.org/10.17226/10176
- Francois Crouzet, “Wars, Blockade, and Economic Change in Europe, 1792-1815,” Journal of Economic History, Vol. 24 (1964).
- Nicholas Tracy, The Naval Chronicle: The Contemporary Record of the Royal Navy at War, Volume III 1804-1806, (London, Stackpole Books, 1999), pp 12-13.
- Brian Lavery, “Nelson’s Navy: The Ships, Men, and Organisation, 1793-1815” (Annapolis, Naval Institute Press, 2000).
- Alfred T. Mahan, Sea Power in Its Relation with the War of 1812 (London, Sampson, Low, Marston & Company, 1905), pp 2-4.
- Robert M. Browning, From Cape Charles to Cape Fear (Tuscaloosa, University of Alabama Press, 1993).
- Jefferson Davis, The Rise and Fall of the Confederate Government Vol. I, (Richmond, De Capo, 1990).
- Stephen R. Wise, Lifeline of the Confederacy (Columbia, University of South Carolina Press, 1988).
- Jason Glab, “Blockading China: A Guide”, https://warontherocks.com/2013/10/blockading-china-a-guide/commentary, October 1, 2013.
- Sean Mirski, “Stranglehold: The Context, Conduct, and Consequences of an American Naval Blockade of China,” Journal of Strategic Studies, http://carnegieendowment.org/2013/02/12/stranglehold-context-conduct-and-consequences-of-american-naval-blockade-of-china-pub-51135, February 12, 2013.
- Edward Ingram, In Defense of British India, (London, A. Wheaton & Co., 1984).
- Noel Mostert, The Line Upon A Wind, (New York, Norton, 2008).
 San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 1994, Section II Art. 93-104
 U.S. Navy Commander’s Operational Law Handbook NWP 1-14M, 2007Pg 4-10.
 Tracy, Nicholas, “The Naval Chronicle: The Contemporary Record of the Royal Navy at War, Volume III 1804-1806,” (London, Stackpole Books, 1999), pp 12-13.
 Brian Lavery, “Nelson’s Navy: The Ships, Men, and Organisation, 1793-1815” (Annapolis, Naval Institute Press, 2000), pg 66.
 Francois Crouzet, “Wars, Blockade, and Economic Change in Europe, 1792-1815,” Journal of Economic History, Vol. 24 (1964): pg 578.
 Alfred T. Mahan, Sea Power in Its Relation with the War of 1812 (London, Sampson, Low, Marston & Company, 1905), pp 2-4.
Ibid, pp 104-108.
 Ibid, pg 110.
 Ibid, pp 114-115.
 Robert M. Browning, From Cape Charles to Cape Fear (Tuscaloosa, University of Alabama Press, 1993), pp 2-3.
 Jefferson Davis, The Rise and Fall of the Confederate Government Vol. I, (Richmond, De Capo, 1990), pp 402-403.
 Stephen R. Wise, Lifeline of the Confederacy (Columbia, University of South Carolina Press, 1988), pg 1.
 Jason Glab, “Blockading China: A Guide”, https://warontherocks.com/2013/10/blockading-china-a-guide/commentary, October 1, 2013
 National Research Council. 2001. Naval Mine Warfare: Operational and Technical Challenges for Naval Forces. Washington, DC: The National Academies Press. https://doi.org/10.17226/10176 Pg 18.
Featured Image: Battle of Mobile Bay (Louis Prang/Wikimedia Commons)