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The Limits of the Naval Blockade

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Battle of Mobile Bay (Louis Prang / Wikimedia Commons)

By CIMSEC 2019-05-01 17:08:53

[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.

Blockading China

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. 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 sunk 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. 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.

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 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.

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 

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?

In 1812, the United States declared war on Great Britain over the issues of sailors’ rights and free trade. Many American seafarers 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 (forced them into military service) from merchant ships. In 1807, the HMS Leopard stopped and searched the U.S. Navy warship USS Chesapeake for deserters, took four and hung one of them. It was a step too far.

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. 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

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. Some were in the naval dockyards, some were stationed across the globe, and vessels stationed overseas would take up to six months to return to the U.S. At the outbreak of war, there were only three vessels ready for service 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 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.

While the blockade grew ever more effective, it was never entirely successful. 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. 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.

Conclusion

In the historical cases above, neither blockade solely won the conflict. 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.

This article appears courtesy of CIMSEC and is reproduced here in an abbreviated form. It may be found in its original edition here

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.